Rocks and fossils

Rocks, minerals and fossils of Michigan

Real photos, what each one is, how old it is, where it turns up, how to spot it, and what it gets confused with.

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Showing 47 of 47

Pumpellyite-(Mg) crystals on quartz, Copper Falls Mine, Keweenaw County (raw mineral, not a polished greenstone)

GemMineralUpper Peninsula

Chlorastrolite (greenstone)

"small rounded beach pebbles showing a finely radiating or stellated pattern of slender crystals." The name means "green star stone"; colors range "from yellowgreen to almost black."

Details

Pumpellyite-(Mg) crystals on quartz, Copper Falls Mine, Keweenaw County (raw mineral, not a polished greenstone) Photo: Robert M. Lavinsky, CC BY-SA 3.0

What it is: Michigan's state gem, "a variety of the mineral pumpellyite." State law: "Chlorastrolite, commonly known as greenstone, is adopted as the official gem of this state." (MCL 2.17, 1972)
Age: Formed in the Keweenaw lava flows of the Midcontinent Rift, which erupted about 1,109 to 1,087 million years ago.
Where: "greenstones form inside the bubble holes in lava flow tops ... on the beaches of the Keweenaw or isle Royale they weather out." Central and Delaware are two places with greenstones on rock dumps.
How to spot it: "small rounded beach pebbles showing a finely radiating or stellated pattern of slender crystals." The name means "green star stone"; colors range "from yellowgreen to almost black."
Look-alikes: Epidote: "Much of the pumpellyite is bluish-green in contrast to the epidote, which is yellow-green."

No collecting at Isle Royale National Park. Mine dumps are private land.

Sources: 1 2 3 4 5

Native copper, Caledonia Mine, Ontonagon County

MineralUpper PeninsulaLower Peninsula

Native copper and float copper

Shiny copper on a fresh surface, heavy, and soft enough to bend. Weathered pieces carry coatings of reddish cuprite, black tenorite or green malachite.

Details and 5 photos

Native copper, Caledonia Mine, Ontonagon County Photo: James St. John, CC BY 2.0
Native copper-coated cobble, Calumet and Hecla Mine, Calumet, museum display Photo: James St. John, CC BY 2.0
Float copper boulder from Michigan, museum display at Tellus Science Museum, Georgia Photo: JJonahJackalope, CC BY-SA 4.0
Native copper, Keweenaw Peninsula Photo: John Mortimore, CC BY-SA 3.0
Glacial (float) copper boulder, near Houghton, museum display Photo: James St. John, CC BY 2.0

What it is: "Native copper is easily the most famous of Michigan's minerals." Masses ranged "up to masses 14 meters long and weighing 382 metric tons." Forms include wire, leaf, "shot", "spike" and "half-breeds."
Age: USGS dates the Keweenaw native copper to between 1,060 and 1,047 million years ago.
Where: "a narrow belt over 150 kilometers long, stretching southwestward through Keweenaw, Houghton, and Ontonagon Counties." Float copper turns up in glacial drift, "particularly in the Northern Peninsula"; a 29 kg float mass was plowed up in southern Tuscola County.
How to spot it: Shiny copper on a fresh surface, heavy, and soft enough to bend. Weathered pieces carry coatings of reddish cuprite, black tenorite or green malachite.
Look-alikes: No look-alikes are published in our checked sources yet.

Mine rock piles are private land.

Sources: 6 7 8

Native silver, Michigan Mine, Ontonagon County

MineralUpper Peninsula

Native silver and half-breeds

Silver-white metal, often next to copper.

Details and 5 photos

Museum specimen Native silver, Michigan Mine, Ontonagon County Photo: James St. John, CC BY 2.0
Copper-silver glacial cobble, Michigan, museum display Photo: James St. John, CC BY 2.0
Copper-silver half-breed, Keweenaw Peninsula, museum display Photo: James St. John, CC BY 2.0
Native silver, Osceola Mine, Keweenaw Peninsula, museum display Photo: James St. John, CC BY 2.0
Native silver, Calumet, Houghton County, Smithsonian specimen Photo: courtesy Smithsonian National Museum of Natural History, CC0 1.0

What it is: "The term 'half-breed' has been used to describe an intergrowth of native silver and native copper."
Age: Not yet in our checked sources.
Where: Copper Country mines. "Placer silver reportedly has been recovered from Lake Superior on the north side of Keweenaw Point."
How to spot it: Silver-white metal, often next to copper.
Look-alikes: Mill-made half-breeds: "most of the nugget-like 'half breed' specimens seen in the marketplace are products of the stamp mills ... A very few of these intergrowths, however, may be natural."

Sources: 9

MineralUpper Peninsula

Lake Superior agate

Bands, a "dull waxy luster", a "pock-marked surface", and light passing through when you "hold them up to the light."

Full guide: Lake Superior agate

Details and 5 photos

Lake Superior agate, lake floor off the Keweenaw Peninsula Photo: James St. John, CC BY 2.0
Lake Superior agate, Lake Superior shoreline, Upper Peninsula Photo: James St. John, CC BY 2.0
Lake Superior agate nodule with visible bands, lake floor off the Keweenaw Peninsula Photo: James St. John, CC BY 2.0
Beach pebbles at Agate Beach, Keweenaw Peninsula Photo: xinem, CC BY 2.0
Cut and polished Lake Superior agate, Minnesota (not a Michigan specimen) Photo: Lech Darski, CC BY-SA 4.0

What it is: "A translucent cryptocrystalline variety of quartz, characterized by colors arranged in alternating stripes or bands."
Age: Formed inside the Midcontinent Rift lavas, which erupted about 1,109 to 1,087 million years ago.
Where: Lake Superior beaches of the Upper Peninsula, plus rivers and gravel pits. Michigan Tech: agates "can be found on most Keweenaw beaches, although they are prized and captured by roving humans." One of the largest ever found, 7.85 kg, came from just south of Horseshoe Harbor.
How to spot it: Bands, a "dull waxy luster", a "pock-marked surface", and light passing through when you "hold them up to the light."
Look-alikes: Jaspilite has bands but is not translucent. Michigan Tech calls agate-like rocks "that are red-brown and featureless" jasper.

Read the full Lake Superior agate guide

Sources: 10 4 11 5

MineralUpper Peninsula

Datolite

"Porcelaneous masses, or nodules, with botryoidal surfaces," from "a few millimeters to 30 centimeters" across. Usually white. "Some datolite may be fluorescent."

Details and 5 photos

Polished datolite nodule, Keweenaw County Photo: Robert M. Lavinsky, CC BY-SA 3.0
Datolite, Isle Royale National Park, Keweenaw County Photo: Robert M. Lavinsky, CC BY-SA 3.0
Polished datolite nodule, Keweenaw County Photo: Robert M. Lavinsky, CC BY-SA 3.0
Slabbed datolite nodule, Centennial Mine, Houghton County Photo: Robert M. Lavinsky, CC BY-SA 3.0
Sawed and polished datolite nodule, Quincy Mine, Hancock, Houghton County Photo: Robert M. Lavinsky, CC BY-SA 3.0

What it is: "A borosilicate mineral ... In Michigan, datolite occurs only in the native copper deposits and their host rocks in the Northern Peninsula."
Age: Not yet in our checked sources.
Where: Houghton and Keweenaw County mines, for example the Mesnard ("Pink, yellow-orange to red nodules"). "Some superb datolite nodules also have been recovered from the floor of Lake Superior, and as pebbles on its beaches."
How to spot it: "Porcelaneous masses, or nodules, with botryoidal surfaces," from "a few millimeters to 30 centimeters" across. Usually white. "Some datolite may be fluorescent."
Look-alikes: No look-alikes are published in our checked sources yet.

Mine sites are private land.

Sources: 12

MineralUpper Peninsula

Thomsonite

Check the look-alikes first: true thomsonite is "far less common" than the pink pebbles often called thomsonite.

Details and 4 photos

Thomsonite pebble from Minnesota's Lake Superior shore (not a Michigan specimen) Photo: Robert M. Lavinsky, CC BY-SA 3.0
Sawed and polished thomsonite with eye pattern, Thomsonite Beach, Grand Marais, Minnesota (not a Michigan specimen) Photo: Robert M. Lavinsky, CC BY-SA 3.0
Thomsonite nodules in basalt; the photo title gives Grand Marais, Minnesota (not a Michigan specimen) Photo: Dave Dyet, Public domain
Small thomsonite eyes weathering out of basalt (locality not given; not a Michigan specimen) Photo: Mike Kestell, CC BY 2.0

What it is: "One of the zeolite group minerals commonly found in vesicles in basalt."
Age: Not yet in our checked sources.
Where: "Lake Superior beaches near Grand Marais" (Alger County), Thomsonite Hill near Eagle Harbor, and the Copper Harbor and Fort Wilkins area. Isle Royale beach pebbles too: "The variety 'lintonite' is pale to dark green." No collecting at Isle Royale (36 CFR 2.1).
How to spot it: Check the look-alikes first: true thomsonite is "far less common" than the pink pebbles often called thomsonite.
Look-alikes: "Beach pebbles of pinkish prehnite ... are often confused with those of thomsonite." An X-ray study of Keweenaw beach "thomsonites" "showed most are either natrolite or mesolite mixed with thomsonite."

Sources: 13 14

Prehnite with native copper, Keweenaw County

MineralUpper Peninsula

Prehnite and "patricianite"

"An intergrowth of pink prehnite, chlorite, and specks of native copper was named 'patricianite'."

Details and 4 photos

Prehnite with native copper, Keweenaw County Photo: Robert M. Lavinsky, CC BY-SA 3.0
Native copper in prehnite, Osceola Mine, Houghton County Photo: Robert M. Lavinsky, CC BY-SA 3.0
Raw and tumbled prehnite side by side (locality not given) Photo: Texas Lane, CC BY-SA 4.0
Native copper in prehnite, Franklin Mine, museum display Photo: Pacific Museum of Earth from Canada, CC BY-SA 2.0

What it is: "Much prehnite is pale apple-green, but can be highly variable in color."
Age: Not yet in our checked sources.
Where: Copper Country. Patricianite is "relatively common as beach pebbles in the Copper Harbor-Fort Wilkins area."
How to spot it: "An intergrowth of pink prehnite, chlorite, and specks of native copper was named 'patricianite'."
Look-alikes: Patricianite "is often mistaken for thomsonite."

Sources: 15

MineralUpper Peninsula

Epidote

EGLE: epidote "is yellow-green," while pumpellyite is "bluish-green."

Details and 3 photos

Epidote-lined vug in basalt, Portage Lake Volcanics, Centennial Mine, Keweenaw Peninsula Photo: James St. John, CC BY 2.0
Epidote-rich beach cobble, Nahant, Massachusetts (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Unakite, a granite with epidote and pink feldspar (locality not given; not a Michigan specimen) Photo: James St. John, CC BY 2.0

What it is: "An abundant and common mineral either of hydrothermal or metamorphic origin." It forms "in veins cutting granites and metamorphic rocks" and "in vesicles in basaltic rocks."
Age: Not yet in our checked sources.
Where: In the Keweenaw native copper deposits "it is abundant in both veins and basaltic lodes." Near Marquette it fills veins in granite at Sugar Loaf Mountain.
How to spot it: EGLE: epidote "is yellow-green," while pumpellyite is "bluish-green."
Look-alikes: Chlorastrolite (pumpellyite). It can share amygdules with epidote, "from which it is not easily distinguished."

No collecting at Isle Royale (36 CFR 2.1). Mine rock piles are private land. State land: 25 lb per person per year (R 299.922(hh)). Rules change; check with the land manager; not legal advice.

Sources: 16 1 17 14

MineralUpper PeninsulaLower Peninsula

Calcite

"Crystals from 5 to 10 centimeters long are fairly common." Some are pink or red from "inclusions of native copper."

Details and 3 photos

Calcite crystals with native copper and silver, Upper Peninsula Photo: James St. John, CC BY 2.0
Calcite crystal with native copper, Upper Peninsula Photo: James St. John, CC BY 2.0
Native copper inside a calcite crystal, Central Mine, Keweenaw Peninsula, museum display Photo: James St. John, CC BY 2.0

What it is: In the Copper Country, "after native copper calcite easily comes first in the interest and beauty of its specimens." Calcite is also "the major mineral constituent of Petoskey stones."
Age: Not yet in our checked sources.
Where: Copper Country mines (Upper Peninsula). Petoskey stones (Lower Peninsula).
How to spot it: "Crystals from 5 to 10 centimeters long are fairly common." Some are pink or red from "inclusions of native copper."
Look-alikes: No look-alikes are published in our checked sources yet.

Mine sites are private land.

Sources: 18

RockUpper Peninsula

Jaspilite (banded iron formation)

Bands of red jasper and hematite. Unlike agate, it is not translucent.

Details and 5 photos

Jaspilite, Jasper Knob, Ishpeming Photo: James St. John, CC BY 2.0
Cut and polished jaspilite, Ironwood Iron-Formation, Wakefield, Gogebic Range Photo: James St. John, CC BY 2.0
Banded iron formation, west of Michigamme Photo: James St. John, CC BY 2.0
Polished jaspilite slab from Michigan, Smithsonian specimen Photo: courtesy Smithsonian National Museum of Natural History, CC0 1.0
Banded iron formation, Dickinson County, Smithsonian specimen Photo: courtesy Smithsonian National Museum of Natural History, CC0 1.0

What it is: "'Jaspilite' (banded red jasper with hematite) is very well developed in ores of this range" (the Marquette Range).
Age: The iron formations formed about 1.9 billion years ago (USGS).
Where: The iron ranges of the western and central Upper Peninsula. Taconite: some iron formations are "amenable to beneficiation (e.g., taconite)"; at the Empire mine, "Magnetitic taconite ore occurs in the Negaunee Iron Formation."
How to spot it: Bands of red jasper and hematite. Unlike agate, it is not translucent.
Look-alikes: Agate. EGLE: "Not an agate - has bands but is not translucent. It is banded jasper and hematite. It is also known as Jaspilite and is very collectable."

"Jasper Knob, Ishpeming: Outstanding outcrop of folded jaspilite ... Please note: collecting is not allowed."

Sources: 11 10 19 20

Hematite, metallic gray variety (locality not given)

MineralUpper Peninsula

Hematite and specularite

"it has a distinctive reddish-brown streak."

Details and 5 photos

Hematite, metallic gray variety (locality not given) Photo: Darla Sondrol, CC0
Black botryoidal hematite, Ishpeming, museum display Photo: James St. John, CC BY 2.0
Specularite (silvery hematite) layered with quartzite, Republic Mine, Marquette County Photo: James St. John, CC BY 2.0
Kidney ore (botryoidal hematite) from Michigan, locality unknown. The yellow spot is lamp glare Photo: DanielCD, CC BY-SA 3.0
Hematite, Marquette County, Smithsonian specimen Photo: courtesy Smithsonian National Museum of Natural History, CC0 1.0

What it is: Hematite is "one of the most important and abundant iron ores." Named forms include "kidney ore", "pencil ore" and "martite."
Age: The iron formations formed about 1.9 billion years ago (USGS).
Where: "found on the Precambrian iron ranges of Michigan's western Upper Peninsula."
How to spot it: "it has a distinctive reddish-brown streak."
Look-alikes: Specularite is "A black or gray variety of hematite with a shiny metallic luster ... Has the same streak."

Sources: 21 10 19

Quartz with native copper, Keweenaw Peninsula

MineralUpper PeninsulaLower Peninsula

Quartz, amethyst, jasper and chert

Goose Lake near Ishpeming gave "well-formed, prismatic, colorless-to-milky crystals over 25 cm in length."

Details and 5 photos

Quartz with native copper, Keweenaw Peninsula Photo: Robert M. Lavinsky, CC BY-SA 3.0
Tumble-polished jasper pebble (locality not given) Photo: Adrian Pingstone, Public domain
Cherty ironstone, Ironwood Formation, Upper Peninsula Photo: Darla Sondrol, CC0 1.0
Beach cobble with a hollow lined with quartz crystals, Lake Superior shoreline, Upper Peninsula Photo: James St. John, CC BY 2.0
Amethyst geode interior, southeastern Brazil (not a Michigan specimen) Photo: James St. John, CC BY 2.0

What it is: Quartz in many forms: clear crystals, purple amethyst, red jasper and chert.
Age: Not yet in our checked sources.
Where: "Horseshoe Harbor: Groups of amethyst crystals"; "Agate Harbor: Agate pebbles and amethyst pebbles." Jasper pebbles on the Keweenaw shore (Seven Mile Point area), and "As chert and jasper in the iron ranges." Chert nodules occur in the Bayport and Traverse limestones. Flint: chert nodules (Huron County area) "were an important source of 'flint' for the Native Americans of the Southern Peninsula."
How to spot it: Goose Lake near Ishpeming gave "well-formed, prismatic, colorless-to-milky crystals over 25 cm in length."
Look-alikes: No look-alikes are published in our checked sources yet.

Worked flint, such as arrowheads or other stone tools, is an artifact, not a rock. Michigan law: "Without the consent of the land owner, a person shall not remove any relics or records of antiquity" (MCL 324.76106). Rules change; check with the land manager; not legal advice.

Sources: 11 22

MineralUpper Peninsula

Gold

"The discovery of gold in Michigan is credited to Douglass Houghton, who, in the early 1840s at an unspecified Northern Peninsula site, panned ... placer gold."

Details and 3 photos

Museum specimen Ore specimen from the Ropes Gold Mine, Ishpeming Photo: Pacific Museum of Earth from Canada, CC BY-SA 2.0
Placer gold pebbles, Washington State, museum display (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Gold in a quartz vein, Geraldton, Ontario, museum display (not a Michigan specimen) Photo: James St. John, CC BY 2.0

What it is: "The discovery of gold in Michigan is credited to Douglass Houghton, who, in the early 1840s at an unspecified Northern Peninsula site, panned ... placer gold."
Age: Not yet in our checked sources.
Where: The Ropes mine near Ishpeming opened in October 1881 and yielded "about $600,000 in gold and $50,000 in silver." About 7 km east of Grand Marais, native copper occurs "As microscopic flakes with gold and rare platinum ... in black sands in sand dunes."
How to spot it: Not yet in our checked sources.
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 23 6

Kimberlite, Lake Ellen outcrop, Upper Peninsula (no diamond shown)

GemRockUpper PeninsulaLower Peninsula

Diamonds and kimberlite

Older USGS view (1981): "No diamonds are known in the Lake Ellen kimberlite, but it has not been adequately sampled."

Details and 4 photos

Kimberlite, Lake Ellen outcrop, Upper Peninsula (no diamond shown) Photo: John F. Green, CC BY-SA 3.0
Kimberlite: a garnet-bearing xenolith from the Lake Ellen Kimberlite, Iron County Photo: James St. John, CC BY 2.0
Rough light brown diamond crystal, 3.7 mm, cut in half (locality not given) Photo: W.carter, CC BY-SA 4.0
Diamond in kimberlite, Kimberley, South Africa, museum display (not a Michigan specimen) Photo: James St. John, CC BY 2.0

What it is: "A few diamonds have been found from time to time in the glacial drift of Wisconsin, Michigan, Indiana, and Ohio."
Age: Kimberlite age is attributed only: Bornhorst says the pipes "were emplaced at about 170 Ma"; USGS gives only "post-Ordovician."
Where: The Dowagiac stone (Cass County) was found in 1894 in a gravel pit and weighed "10.875 carats." "By the early 1900s some 25 to 30 stones had been found." "More than 20 kimberlites have been discovered since 1971 ... Many kimberlites in Northern Michigan contain diamonds" (Mineralogy of Michigan, 2004).
How to spot it: Older USGS view (1981): "No diamonds are known in the Lake Ellen kimberlite, but it has not been adequately sampled."
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 24 25 26

MineralLower Peninsula

Gypsum, selenite and satin spar

"hardness of 2, can be scratched by a fingernail."

Details and 4 photos

Museum specimen Gypsum, Grand Rapids Photo: Pacific Museum of Earth from Canada, CC BY-SA 2.0
Clear selenite gypsum, 8 cm (locality not given) Photo: Darla Sondrol, CC0 1.0
Satin spar gypsum, near Derby, England (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Alabaster, a fine-grained gypsum, from Michigan per the source description Photo: Darla Sondrol, CC0 1.0

What it is: Gypsum and its clear (selenite) and fibrous (satin spar) forms.
Age: Not yet in our checked sources.
Where: It "is mined near Tawas City and has been mined near Grand Rapids." Alabaster (Iosco County) produces "salmon-colored selenite crystals." Grandville produces fibrous "satin spar." "One selenite crystal in the Grand Rapids Museum is 60 cm in diameter and 120 cm long."
How to spot it: "hardness of 2, can be scratched by a fingernail."
Look-alikes: No look-alikes are published in our checked sources yet.

Quarries are private land.

Sources: 10 27

MineralLower Peninsula

Halite (rock salt)

"Single crystals half a meter or more across are known."

Details and 3 photos

Halite (rock salt), Salina Group, Detroit Photo: James St. John, CC BY 2.0
Rock salt, Salina Group, Detroit Photo: James St. John, CC BY 2.0
Rock salt, Salina Group, Detroit (second sample) Photo: James St. John, CC BY 2.0

What it is: Rock salt. "Michigan was the leading salt-producing state in the United States for many years."
Age: Silurian. The Salina Group salt beds "measure nearly 900 meters in thickness, over 600 of which is rock salt."
Where: Under the Lower Peninsula, about "25,000 cubic kilometers of rock salt." Rock salt "is mined under the city of Detroit"; the Detroit mine "began producing salt in 1910" and is Michigan's only salt mine, mining "at 317 meters" (about 1,040 feet).
How to spot it: "Single crystals half a meter or more across are known."
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 28 29 30

Celestine crystal, Woolmith (Scofield) Quarry, Monroe County

MineralLower PeninsulaUpper Peninsula

Celestine and fluorite

Celestine crystals are "pale blue in color, some transparent."

Details and 5 photos

Celestine crystal, Woolmith (Scofield) Quarry, Monroe County Photo: Robert M. Lavinsky, CC BY-SA 3.0
Celestine crystals, South Rockwood Photo: James St. John, CC BY 2.0
Yellow sulfur crystals with celestine, Maybee, Monroe County Photo: James St. John, CC BY 2.0
Celestine crystals, Holloway (Rockwood) Quarry, Monroe County Photo: Robert M. Lavinsky, CC BY-SA 3.0
Fluorite with calcite, Newport Quarry, Monroe County Photo: Robert M. Lavinsky, CC BY-SA 3.0

What it is: The Woolmith quarry (Monroe County) is "One of the classic U.S. localities for celestine."
Age: Not yet in our checked sources.
Where: Celestine: Woolmith quarry, Rockwood (Wayne County) and Drummond Island. Fluorite: "in vugs in limestones" near Bay City and near Newport (Monroe County), in Gogebic County gneiss, and near Eagle River.
How to spot it: Celestine crystals are "pale blue in color, some transparent."
Look-alikes: No look-alikes are published in our checked sources yet.

Quarries are private land.

Sources: 31 32

Yooperlite cobble under UV light, Lake Superior shore, Upper Peninsula

RockUpper Peninsula

Yooperlite® (sodalite syenite)

EGLE recommends a 365 nm UV light and names classes such as "Gemmy" and "Galaxy."

Details and 4 photos

Yooperlite cobble under UV light, Lake Superior shore, Upper Peninsula Photo: James St. John, CC BY 2.0
Yooperlite cobble, about 7.6 cm, Lake Superior shoreline, Upper Peninsula Photo: James St. John, CC BY 2.0
The same Yooperlites under UV light (top) and in normal light (bottom) (locality not given) Photo: TR15336300101, CC BY-SA 4.0
Yooperlite under UV light, with orange-glowing sodalite, Lake Superior shoreline, Upper Peninsula Photo: James St. John, CC BY 2.0

What it is: EGLE: "a fluorescent rock (Sodalite syenite) that glows 'in the dark' under ultraviolet light. The rock first became known when a U.P. resident discovered them in 2017." The Ontario Geological Survey: the syenite contains "orange fluorescing hackmanite, a variety of sodalite."
Age: Not yet in our checked sources.
Where: They "are actually from Canada! ... near Marathon, Ontario known as the Coldwell Alkaline Complex," carried here by glaciers.
How to spot it: EGLE recommends a 365 nm UV light and names classes such as "Gemmy" and "Galaxy."
Look-alikes: Granite. In normal light "a Yooperlite® looks like granite."

Sources: 10 33

RockUpper PeninsulaLower Peninsula

Puddingstone

White quartzite with red jasper pebbles.

Details and 5 photos

Drummond Island puddingstone Photo: PaulDonelson, CC BY-SA 3.0
Large puddingstone boulder, Drummond Island Photo: Corvair Owner, CC BY-SA 2.0
Jasper conglomerate, or St. Joseph Island puddingstone, St. Joseph Island, Ontario (not a Michigan specimen) Photo: Kdorse, CC BY-SA 3.0
Jasper-quartz pebble conglomerate, Lorrain Formation, Ontario, the bedrock source of puddingstone (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Conglomerate with red jasper pebbles from Michigan, Smithsonian specimen Photo: courtesy Smithsonian National Museum of Natural History, CC0 1.0

What it is: "a quartzite conglomerate with bright red jasper inclusions."
Age: The Lorrain Formation jasper conglomerate "is 2,200 - 2,450 million years old ... part of the Huronian supergroup."
Where: Locals call it "'Michigan puddingstone' or 'Drummond Island puddingstone'." Glaciers carried it "as far away as Southwest Iowa!"
How to spot it: White quartzite with red jasper pebbles.
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 10 34

Omarolluk rocks at their source, Belcher Islands, Hudson Bay

RockUpper Peninsula

Omars

Round holes "between a half inch and 3 inches in diameter."

Details

Omarolluk rocks at their source, Belcher Islands, Hudson Bay Photo: Mike Beauregard from Nunavut, Canada, CC BY 2.0

What it is: "Omars have a color and texture like Keweenawan basalts, but they are fine-grained sedimentary rocks."
Age: Not yet in our checked sources.
Where: Keweenaw beaches. "Omars were carried more than 700 miles by the continental glaciers, from Omarolluk Sound in the Belcher Islands of Hudson Bay."
How to spot it: Round holes "between a half inch and 3 inches in diameter."
Look-alikes: Keweenaw basalt, which has a similar color and texture.

Sources: 4

Granitic glacial erratic, Porcupine Mountains Wilderness State Park

RockUpper PeninsulaLower Peninsula

Granite and other glacial erratics

Light colored and crystalline.

Details and 4 photos

Granitic glacial erratic, Porcupine Mountains Wilderness State Park Photo: Curtis Abert, CC BY 2.0
Glacial erratic boulder, Bunker Nature Preserve, Aurelius Township, Ingham County Photo: Tim Kiser, CC BY-SA 4.0
Mixed beach stones, Pictured Rocks National Lakeshore Photo: National Park Service, Public domain
Granite pebble from a glacial-era lake deposit, west of Givens, Ohio (not a Michigan specimen) Photo: James St. John, CC BY 2.0

What it is: Michigan Tech: "Granite is a broad name used for light colored crystalline rocks that are present as glacially transported rocks in the Keweenaw."
Age: Not yet in our checked sources.
Where: Statewide. EGLE: erratics "can be larger than your car." "the most commonly sought-after glacial erratics by rockhounds include puddingstones, lightning stones, Yooperlites®, or Lake Superior agates." EGLE also pictures a "Gowganda tillite."
How to spot it: Light colored and crystalline.
Look-alikes: Yooperlites look like granite in daylight.

Sources: 4 10

RockUpper Peninsula

Rhyolite

Smooth, hard, usually reddish beach stones.

Details and 4 photos

Rhyolite beach on Lake Superior Photo: S. J. G., CC BY-SA 4.0
Felsite (rhyolite) conglomerate with copper, Kingston Mine, Keweenaw County Photo: James St. John, CC BY 2.0
Rhyolite conglomerate with native copper, Upper Peninsula Photo: Darla Sondrol, CC0 1.0
Pink rhyolite (locality not given) Photo: Michael C. Rygel, CC BY-SA 3.0

What it is: "Rhyolite is a hard rock and makes smooth beach stones, usually reddish in color."
Age: Not yet in our checked sources.
Where: Keweenaw. Mount Houghton "is the highest point in the peninsula," and the red area on Michigan Tech's map "is a volcanic dome." Rhyolite porphyry, with quartz phenocrysts, is recorded near Michigamme (Seaman Mineral Museum: "rhyolite porphyry (Clements, 1895)"). In Houghton and Keweenaw counties, feldspar occurs "As both phenocrysts and in the matrix of felsite."
How to spot it: Smooth, hard, usually reddish beach stones.
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 4 11 35

RockUpper Peninsula

Basalt and amygdaloid

"Porphyritic basalt, sometimes called 'turkey track' ... Look for it near Keweenaw Point."

Details and 4 photos

Amygdaloidal basalt, Keweenaw Peninsula Photo: James St. John, CC BY 2.0
Amygdaloidal basalt, Delaware Mine, Keweenaw Photo: James St. John, CC BY 2.0
Copper-bearing amygdaloidal basalt, Keweenaw Peninsula, museum display Photo: James St. John, CC BY 2.0
Ophite (ophitic basalt), Greenstone Flow, Keweenaw, Smithsonian specimen Photo: courtesy Smithsonian National Museum of Natural History, CC0 1.0

What it is: The lava rock of the Midcontinent Rift. Agates and greenstones formed in its bubble holes.
Age: The rift lavas erupted about 1,109 to 1,087 million years ago (USGS).
Where: Keweenaw beaches. "Ophitic basalt or Ophite ... common in the Keweenaw, and rare elsewhere." Diabase and dolerite: "Pegmatoid, pegmatitic basalt or dolerite is also found in the Keweenaw, and is very rare elsewhere." EGLE: Michigan's Precambrian volcanics were "accompanied by dikes of diabase and gabbro."
How to spot it: "Porphyritic basalt, sometimes called 'turkey track' ... Look for it near Keweenaw Point."
Look-alikes: Omars have a color and texture like Keweenaw basalt.

Sources: 4 5 30

Jacobsville Sandstone from Jacobsville, Michigan, A. E. Seaman Mineral Museum

RockUpper PeninsulaLower Peninsula

Sandstone and Jacobsville Sandstone

Keweenaw sandstones "are reddish or rusty, with white layers and spots. They tend to form flat pebbles and cobbles." The red parts were "rusted (oxidized) by groundwater."

Details and 5 photos

Museum specimen Jacobsville Sandstone from Jacobsville, Michigan, A. E. Seaman Mineral Museum Photo: Chris857, CC BY-SA 3.0
Jacobsville Sandstone, Jacobsville, museum display Photo: Chris857, CC BY-SA 3.0
White Munising Formation over Jacobsville Sandstone, Pictured Rocks National Lakeshore Photo: Chris857, CC BY-SA 3.0
Sandstone with fossil bivalves, Marshall Sandstone, near Jackson Photo: James St. John, CC BY 2.0
Red sandstone, Houghton County, Smithsonian specimen Photo: courtesy Smithsonian National Museum of Natural History, CC0 1.0

What it is: Michigan Tech: "Sandstone is made of sand particles," from 0.0625 mm to 2 mm across.
Age: The Jacobsville is Precambrian, "the youngest of the area's Precambrian rocks, but the exact age is unknown." It is older than about 542 million years. EGLE lists sandstone among Michigan's Cambrian, Mississippian and Pennsylvanian rocks too.
Where: Michigan Tech: "The Keweenaw Bay shorelines have many cliff exposures of Jacobsville Sandstone."
How to spot it: Keweenaw sandstones "are reddish or rusty, with white layers and spots. They tend to form flat pebbles and cobbles." The red parts were "rusted (oxidized) by groundwater."
Look-alikes: No look-alikes are published in our checked sources yet.

No collecting at Pictured Rocks (36 CFR 2.1). State land: 25 lb per person per year (R 299.922(hh)). Rules change; check with the land manager; not legal advice.

Sources: 36 37 30 17 14

Dolostone breccia, Mackinac Breccia, near St. Ignace (museum display at Wittenberg University)

RockLower PeninsulaUpper Peninsula

Limestone and dolomite (dolostone)

Carbonate rocks. The mineral dolomite "is the dominant species in dolostone, and is abundant in many limestones, marbles, iron formations, and hydrothermal veins." Many Michigan fossils, such as corals, "had a hard calcium carbonate skeleton."

Details and 5 photos

Museum specimen Dolostone breccia, Mackinac Breccia, near St. Ignace (museum display at Wittenberg University) Photo: James St. John, CC BY 2.0
Charlevoix Limestone, Sunset Park, Petoskey Photo: James St. John, CC BY 2.0
Stromatolitic dolostone, Kona Dolomite, Lindberg Quarry, Marquette Photo: James St. John, CC BY 2.0
Arch Rock, a limestone breccia arch on Mackinac Island Photo: Hitsandmisses1, CC BY-SA 4.0
Limestone, Saginaw County, Smithsonian specimen Photo: courtesy Smithsonian National Museum of Natural History, CC0 1.0

What it is: Carbonate rocks. The mineral dolomite "is the dominant species in dolostone, and is abundant in many limestones, marbles, iron formations, and hydrothermal veins." Many Michigan fossils, such as corals, "had a hard calcium carbonate skeleton."
Age: EGLE lists limestone and dolomite among Michigan's Devonian and Mississippian rocks, and limestone among its Pennsylvanian rocks.
Where: MGS: Devonian "Natural outcrops and quarries are relatively abundant," for example at Charlevoix, Squaw Bay (Alpena) and Rogers City. DNR: Rockport State Recreation Area has "a fascinating past as a limestone quarry."
How to spot it: Not yet in our checked sources.
Look-alikes: No look-alikes are published in our checked sources yet.

State land: 25 lb per person per year (R 299.922(hh)). DNR, Rockport: "there's no metal detecting in the park." Rules change; check with the land manager; not legal advice.

Sources: 38 30 39 40 41 17

Staurolite-muscovite schist, Michigamme Formation, near Michigamme (Seaman Mineral Museum display)

RockUpper PeninsulaLower Peninsula

Gneiss, schist, slate and quartzite

Metamorphic rocks: rocks changed by heat and pressure. EGLE: in Michigan's Precambrian, "basalt became greenstone; granite became granitic gneiss; sandstone was converted to quartzite; limestone to marble; and shale became slate or mica schist."

Details and 4 photos

Museum specimen Staurolite-muscovite schist, Michigamme Formation, near Michigamme (Seaman Mineral Museum display) Photo: James St. John, CC BY 2.0
Watersmeet Gneiss, about 3.56 billion years old, Watersmeet, museum display Photo: James St. John, CC BY 2.0
Chlorite schist, Michigamme Mine area, Upper Peninsula Photo: James St. John, CC BY 2.0
Quartzite, Marquette South Outcrop Photo: James St. John, CC BY 2.0

What it is: Metamorphic rocks: rocks changed by heat and pressure. EGLE: in Michigan's Precambrian, "basalt became greenstone; granite became granitic gneiss; sandstone was converted to quartzite; limestone to marble; and shale became slate or mica schist."
Age: Precambrian (EGLE).
Where: Upper Peninsula bedrock (EGLE), and as glacial erratics. Michigan Tech: "Large parts of Ontario are underlain by granite and gneiss."
How to spot it: Not yet in our checked sources.
Look-alikes: No look-alikes are published in our checked sources yet.

State land: 25 lb per person per year (R 299.922(hh)). Rules change; check with the land manager; not legal advice.

Sources: 30 42 43 17

Bituminous coal, Upper Freeport Coal, Linton, Ohio (not a Michigan specimen)

RockLower Peninsula

Michigan coal

MSU: Michigan coal has "a weak structure that makes the coal break down into powder when transported."

Details and 3 photos

Bituminous coal, Upper Freeport Coal, Linton, Ohio (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Bituminous coal (locality not given) Photo: Nessa Eull, CC0 1.0
Bituminous coal close-up (locality not given) Photo: Amcyrus2012, CC BY 4.0

What it is: A rock made from buried swamp plants. MSU: the plant remains "changed to peat, were buried" and "have become the coal beds and shales of the central counties." Michigan "produced some 46 million short tons of coal between 1860 and 1949."
Age: Pennsylvanian. USBM: "All of Michigan's past coal production has come from rocks of Pennsylvanian age."
Where: EGLE: "Michigan's coal basin is in the lower peninsula." MSU: mining was "concentrated in Bay, Saginaw, Tuscola and Genesee Counties."
How to spot it: MSU: Michigan coal has "a weak structure that makes the coal break down into powder when transported."
Look-alikes: No look-alikes are published in our checked sources yet.

EGLE: "the last active mines closed in the 1950s." Old mine sites are private land. On state land, coal counts as rock under the 25 lb per person per year limit (R 299.922(hh)). Rules change; check with the land manager; not legal advice.

Sources: 44 45 46 17

Cut and polished septarian nodule slab. The location, near Holland, Michigan, comes from the uploader only

Rock

Lightning stones

"Lightning stones were formerly known as septarian nodules."

Details and 4 photos

Cut and polished septarian nodule slab. The location, near Holland, Michigan, comes from the uploader only Photo: LadyOfManyTalents, CC0
Septarian concretion, Ohio Shale, Columbus, Ohio (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Cut septarian nodule, San Juan County, Utah, museum display (not a Michigan specimen) Photo: Tony Hisgett, CC BY 2.0
Septarian nodule, Nacimiento Mine, New Mexico (not a Michigan specimen) Photo: Kent G. Budge, CC0 1.0

What it is: "Lightning stones were formerly known as septarian nodules."
Age: Not yet in our checked sources.
Where: Their Michigan source has not been confirmed by an official source yet.
How to spot it: Not yet in our checked sources.
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 10

Allegan meteorite fragment (2.9 g). The Allegan meteorite fell in Allegan County, Michigan, in 1899

RockUpper PeninsulaLower Peninsula

Meteorites

MSU has a "MeteorWrong" page about look-alikes.

Details and 4 photos

Allegan meteorite fragment (2.9 g). The Allegan meteorite fell in Allegan County, Michigan, in 1899 Photo: Jon Taylor, CC BY-SA 2.0
Small iron meteorite, 5 cm, 77 g (locality not given) Photo: Jud McCranie, CC BY-SA 4.0
NWA 6927 meteorite from Northwest Africa, with black fusion crust (not a Michigan specimen) Photo: Jon Taylor, CC BY-SA 2.0
Rose City meteorite, which fell in Ogemaw County in 1921, Smithsonian specimen Photo: courtesy Smithsonian National Museum of Natural History, CC0 1.0

What it is: MSU: "Michigan is home to eleven of these wayward space travelers": Allegan, Coleman, Edmore, Grand Rapids, Hamburg, Iron River, Kalkaska, Reed City, Rose City, Seneca Township and Worden.
Age: Not yet in our checked sources.
Where: Hamburg: "Observed Fall: January 16, 2018"; an "Ordinary Chondrite (H4)" recovered "from the frozen lake surfaces within Hamburg Township." Edmore (Montcalm County): "Found: 1939; Classified: 2018"; "Iron (IIIAB)"; "10.22 kg"; "Used as a door stop to the barn."
How to spot it: MSU has a "MeteorWrong" page about look-alikes.
Look-alikes: See MSU's MeteorWrong page.

No collecting at national lakeshores or Isle Royale.

Sources: 47

FossilLower Peninsula

Petoskey stone

"Several star-like features surrounding a central pillar"; "Large unevenly shaped hexagonal openings (corallites) with thin lines radiating from the pillar, like bike spokes"; "Often grow in small dome shapes."

Full guide: Petoskey stone

Details and 5 photos

Polished Petoskey stone (Hexagonaria), Michigan Photo: James St. John, CC BY 2.0
Wet stones, including Petoskey stones, Good Harbor Bay Photo: Debchristiansen, CC BY-SA 4.0
Rough, unpolished Petoskey stones from Michigan Photo: Adam Kelliher / Rubble Rock and Gem, CC BY-SA 4.0
Hexagonaria coral, Lake Michigan shoreline near Bay View, museum display Photo: James St. John, CC BY 2.0
Polished Petoskey stone, Leelanau County, Smithsonian specimen Photo: courtesy Smithsonian National Museum of Natural History, CC0 1.0

What it is: A fossil colonial coral. "The Petoskey stone is hereby adopted as the official stone of the state of Michigan" (1965 PA 89).
Age: "Middle Devonian (393 - 382 million years ago)."
Where: "Gravel Point Formation (Traverse Group) in Charlevoix, Emmet, Cheboygan, Presque Isle, and Alpena" Counties.
How to spot it: "Several star-like features surrounding a central pillar"; "Large unevenly shaped hexagonal openings (corallites) with thin lines radiating from the pillar, like bike spokes"; "Often grow in small dome shapes."
Look-alikes: Charlevoix stone (Favosites): "Series of boxes that build upon one another with horizontal bars called tabulae."

No collecting at Sleeping Bear Dunes National Lakeshore.

Read the full Petoskey stone guide

Sources: 48 18 2

Favosites (Silurian), Mackinac County, Michigan, Smithsonian National Museum of Natural History (a Silurian specimen, not a Devonian Charlevoix-area stone)

FossilLower Peninsula

Charlevoix stone (Favosites)

"Series of boxes that build upon one another with horizontal bars called tabulae"; "Closely packed hexagonal openings (corallites)"; "Often grow in a dome shape."

Details and 3 photos

Museum specimen Favosites (Silurian), Mackinac County, Michigan, Smithsonian National Museum of Natural History (a Silurian specimen, not a Devonian Charlevoix-area stone) Photo: Smithsonian National Museum of Natural History, CC0
Polished Favosites, Iowa City, Iowa, museum display (not a Michigan specimen) Photo: Tim Evanson, CC BY-SA 2.0
Favosites with petroleum, Dundee Formation, Paulding County, Ohio (not a Michigan specimen) Photo: James St. John, CC BY 2.0

What it is: A tabulate coral. EGLE: "Favosites (tabulate coral) (also colloquially called Charlevoix stone)."
Age: Favosites "lived from the Ordovician to the Permian (450-251 million years ago)." The Michigan specimens U-M shows are "Middle Devonian (393 - 382 million years ago)."
Where: Lower Peninsula beaches and Devonian rocks.
How to spot it: "Series of boxes that build upon one another with horizontal bars called tabulae"; "Closely packed hexagonal openings (corallites)"; "Often grow in a dome shape."
Look-alikes: Petoskey stone, which has a central pillar with spokes.

Sources: 48 41

Solitary rugose (horn) coral (locality not given)

FossilLower PeninsulaUpper Peninsula

Horn corals

"Conical or horn-like shape", "Radiating septa (wagon-wheel like appearance)", "Gentle curve to the horn shape."

Details and 4 photos

Solitary rugose (horn) coral (locality not given) Photo: James St. John, CC BY 2.0
Horn coral Siphonophrentis gigantea, White Sulphur, Ohio, museum display (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Horn coral Heliophyllum halli, Bethany Center, New York (not a Michigan specimen) Photo: Wilson44691, CC0 1.0
Weathered-out horn corals, Richmond, Indiana (not a Michigan specimen) Photo: Jstuby, CC0 1.0

What it is: Solitary rugose corals.
Age: "In Michigan, horn corals can be found in rocks ranging from the Ordovician to Mississippian (485 - 323 million years ago)."
Where: Paleozoic rocks of the Michigan Basin.
How to spot it: "Conical or horn-like shape", "Radiating septa (wagon-wheel like appearance)", "Gentle curve to the horn shape."
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 48

Halysites (chain coral), Mackinac County, Michigan, Smithsonian National Museum of Natural History

FossilLower PeninsulaUpper Peninsula

Pipe and chain corals

EGLE lists "Syringopora (pipe-coral)" and "Halysites (chain coral)." Michigan corals belong to "two entirely extinct groups called tabulate corals and rugose corals."

Details and 4 photos

Museum specimen Halysites (chain coral), Mackinac County, Michigan, Smithsonian National Museum of Natural History Photo: Smithsonian National Museum of Natural History, CC0
Polished Halysites chain coral, Gotland, Sweden (not a Michigan specimen) Photo: Hannes Grobe/AWI, CC BY 4.0
Weathered Halysites chain coral, Fairborn, Ohio, museum display (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Halysites chain coral close-up (locality not given) Photo: Wilson44691, Public domain

What it is: EGLE lists "Syringopora (pipe-coral)" and "Halysites (chain coral)." Michigan corals belong to "two entirely extinct groups called tabulate corals and rugose corals."
Age: Not yet in our checked sources.
Where: Michigan beaches and Paleozoic rocks.
How to spot it: Not yet in our checked sources.
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 41

Branching tabulate coral (Thamnopora) in section, Oxford University Museum of Natural History (not a Michigan specimen)

FossilLower PeninsulaUpper Peninsula

Branching coral

"Branching structure with corallites (polyp openings)."

Details

Museum specimen Branching tabulate coral (Thamnopora) in section, Oxford University Museum of Natural History (not a Michigan specimen) Photo: the paleobear from Lontananza, Loreto, Peru, CC BY 2.0

What it is: A branching fossil coral.
Age: Found in Michigan rocks from the Ordovician to the Mississippian (485 to 323 million years ago).
Where: Paleozoic rocks of the Michigan Basin.
How to spot it: "Branching structure with corallites (polyp openings)."
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 48

Stromatoporoid with mamelons, Northport area, Michigan

FossilLower Peninsula

Stromatoporoids (sponges)

"Bumps on exterior are called mammelons," plus "Horizontal layers (lamellae)" with pillars. EGLE spells it "mamelons."

Details and 5 photos

Stromatoporoid with mamelons, Northport area, Michigan Photo: James St. John, CC BY 2.0
Stromatoporoid cross-section, Sunset Park, Petoskey Photo: James St. John, CC BY 2.0
Stromatoporoid, Sunset Park, Petoskey Photo: James St. John, CC BY 2.0
Stromatoporoid, Emmet County, Smithsonian specimen Photo: courtesy Smithsonian National Museum of Natural History, CC0 1.0
Stromatopora, Emmet County, Smithsonian specimen Photo: courtesy Smithsonian National Museum of Natural History, CC0 1.0

What it is: Fossil sponges.
Age: "most commonly found in Devonian rock (about 390 million years ago)."
Where: Lower Peninsula Devonian rocks and beaches.
How to spot it: "Bumps on exterior are called mammelons," plus "Horizontal layers (lamellae)" with pillars. EGLE spells it "mamelons."
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 48 41

Fossil bryozoan (Fenestellidae), Belgium (not a Michigan specimen)

FossilLower PeninsulaUpper Peninsula

Bryozoans

"tiny, near pin-prick sized holes."

Details and 4 photos

Fossil bryozoan (Fenestellidae), Belgium (not a Michigan specimen) Photo: Dwergenpaartje, CC BY-SA 3.0
Branching bryozoan colony, Frankfort, Illinois (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Archimedes, a screw-shaped bryozoan, in limestone (locality not given) Photo: James St. John, CC BY 2.0
Bryozoan pieces in limestone, Warren County, Ohio (not a Michigan specimen) Photo: James St. John, CC BY 2.0

What it is: Colonial animals "more closely related to brachiopods" than to corals.
Age: Not yet in our checked sources.
Where: Michigan beaches.
How to spot it: "tiny, near pin-prick sized holes."
Look-alikes: Petoskey and Charlevoix stones.

Sources: 41

Crinoid head (calyx), Pyrenocrinus buehlerorum, Alpena County, Michigan, Smithsonian National Museum of Natural History. It shows the head, not the stem pieces you usually find on beaches

FossilLower PeninsulaUpper Peninsula

Crinoids (sea lilies)

"you are much more likely to find disarticulated segments than a whole crinoid." Stem pieces (columnals) can be "round, donut-shaped, star-shaped, or pentameral."

Details and 4 photos

Museum specimen Crinoid head (calyx), Pyrenocrinus buehlerorum, Alpena County, Michigan, Smithsonian National Museum of Natural History. It shows the head, not the stem pieces you usually find on beaches Photo: Smithsonian National Museum of Natural History, CC0
Beach-found crinoid stem pieces, Alliklepa beach, Estonia (not a Michigan specimen) Photo: ErikAbner, CC BY 4.0
Crinoid stem pieces in limestone, Saaremaa, Estonia (not a Michigan specimen) Photo: ErikAbner, CC BY 4.0
Complete crinoid crown, Arthroacantha, Silica Shale, Sylvania, Ohio, museum display (not a Michigan specimen) Photo: James St. John, CC BY 2.0

What it is: Sea lilies.
Age: U-M: in Michigan, crinoid material is found in rocks "ranging from the Ordovician to Mississippian" (485 to 323 million years ago), and is "commonly found in Middle Devonian" rocks (393 to 382 million years ago).
Where: Michigan beaches.
How to spot it: "you are much more likely to find disarticulated segments than a whole crinoid." Stem pieces (columnals) can be "round, donut-shaped, star-shaped, or pentameral."
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 41 49

FossilLower Peninsula

Blastoids

"Usually five petal like structures called ambulacra" on a "round rose bud shaped body called a theca." Placoblastus and its relatives "are shaped like tiny blimps."

Details and 4 photos

Nucleocrinus elegans blastoids, Silica Formation, near Paulding, Ohio (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Blastoid head, Elaeacrinus, Columbus Limestone, Ohio (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Pentremites blastoid, Kentucky (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Pentremites blastoid, bottom view; the file gives Kentucky and Illinois (not a Michigan specimen) Photo: Wilson44691, CC0 1.0

What it is: Blastoids are "a group of echinoderms (marine animals like star fish, sea lilies, and sea cucumbers) that lived in Paleozoic seas." U-M: "Sea lilies and blastoids are common finds in Michigan."
Age: U-M: the Michigan blastoid Placoblastus obovatus is found in Middle Devonian rocks (393 to 382 million years ago).
Where: Middle Devonian rocks of Michigan. No public collecting spot for blastoids is named in our checked sources yet.
How to spot it: "Usually five petal like structures called ambulacra" on a "round rose bud shaped body called a theca." Placoblastus and its relatives "are shaped like tiny blimps."
Look-alikes: Crinoids (sea lilies). U-M: "Blastoids look similar to their relatives, the crinoids (sea lilies), but their bodies are constructed in different ways."

State land: invertebrate fossils count toward the 25 lb per person per year limit (R 299.922(hh)). No collecting at Sleeping Bear Dunes, Pictured Rocks or Isle Royale (36 CFR 2.1). Rules change; check with the land manager; not legal advice.

Sources: 49 17 14

FossilLower PeninsulaUpper Peninsula

Brachiopods

"the left and right side should be a mirror image of each other, which is never the case with clams."

Details and 5 photos

Brachiopods in limestone, Gravel Point Formation, near Charlevoix Photo: James St. John, CC BY 2.0
Pentamerid brachiopod, Schoolcraft Dolomite, Garden Peninsula Photo: James St. John, CC BY 2.0
Pentamerid brachiopods, Schoolcraft Dolomite, Garden Peninsula Photo: James St. John, CC BY 2.0
Spirifer brachiopod valve, 18 mm, collected in the Michigan area Photo: Dwergenpaartje, CC BY-SA 3.0
Leptaena brachiopod in limestone, Columbus, Ohio (not a Michigan specimen) Photo: James St. John, CC BY 2.0

What it is: Shelled animals with "two shells or valves." Example genus: Atrypa.
Age: U-M: in Michigan, brachiopods are found in rocks "ranging from the Ordovician to Mississippian" (485 to 323 million years ago).
Where: Michigan beaches and limestones.
How to spot it: "the left and right side should be a mirror image of each other, which is never the case with clams."
Look-alikes: Clams. "if you find a fossil that looks like a clam, it's most likely a brachiopod!"

Sources: 41 50

Fossil gastropod in Columbus Limestone, Kelleys Island, Ohio (not a Michigan specimen)

FossilLower PeninsulaUpper Peninsula

Fossil snails (gastropods)

Most have "an apex, or a tip top where the spiral of the shell ends," an opening where the body came out, and growth lines that can be faint or strong.

Details and 4 photos

Fossil gastropod in Columbus Limestone, Kelleys Island, Ohio (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Fossil snail Euryzone in Dundee Limestone, Ohio (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Beach-found fossil snails, Ontika beach, Estonia (not a Michigan specimen) Photo: ErikAbner, CC BY 4.0
Fossil snails with a pencil for scale, from a Glacier National Park photo set (not a Michigan specimen) Photo: Glacier National Park (National Park Service), Public domain

What it is: Sea snails, "members of the class Gastropoda, which includes land snails and slugs." In Michigan, "many fossil snails are internal casts or replicas made from mud that infilled the shell."
Age: U-M: in Michigan, sea snails are found in rocks "ranging from the Ordovician to Mississippian" (485 to 323 million years ago).
Where: Michigan rocks of Ordovician to Mississippian age. No public collecting spot for snails is named in our checked sources yet.
How to spot it: Most have "an apex, or a tip top where the spiral of the shell ends," an opening where the body came out, and growth lines that can be faint or strong.
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 50 17 14

FossilLower PeninsulaUpper Peninsula

Trilobites

Segmented and "three-lobed." "you are more likely to find broken fragments of trilobites than a whole one."

Details and 4 photos

Phacops rana trilobite, Silica Shale near Sylvania, Ohio (not a Michigan specimen) Photo: Dwergenpaartje, CC BY-SA 3.0
Trilobite Eldredgeops, Silica Shale, Sylvania, Ohio, museum display (not a Michigan specimen) Photo: Daderot, CC0 1.0
Trilobite Phacops rana, Silica, Ohio, museum display (not a Michigan specimen) Photo: Daderot, CC0 1.0
Trilobite Phacops rana, Silica Formation, Ohio, museum display (not a Michigan specimen) Photo: James St. John, CC BY 2.0

What it is: "in the ancient seas of the Michigan Basin, trilobites were king."
Age: Not yet in our checked sources.
Where: Michigan beaches, usually in pieces.
How to spot it: Segmented and "three-lobed." "you are more likely to find broken fragments of trilobites than a whole one."
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 41

Straight-shelled fossil nautiloid (Treptoceras), Upper Ordovician, northern Kentucky (not a Michigan specimen)

FossilLower PeninsulaUpper Peninsula

Nautiloids

"While fossil coiled nautiloids can be found, the straight-shelled variety is more common."

Details and 4 photos

Straight-shelled fossil nautiloid (Treptoceras), Upper Ordovician, northern Kentucky (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Beach-found nautiloid, Ontika beach, Estonia (not a Michigan specimen) Photo: ErikAbner, CC BY 4.0
Straight-shelled nautiloid showing its chambers (locality not given) Photo: James St. John, CC BY 2.0
Polished straight-shelled nautiloids (orthocones) (locality not given) Photo: Deidre Woollard, CC BY 2.0

What it is: "fossil nautiloids are cephalopods with chambered shells they used to control buoyancy."
Age: Not yet in our checked sources.
Where: Michigan beaches.
How to spot it: "While fossil coiled nautiloids can be found, the straight-shelled variety is more common."
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 41

Pyritized brachiopod (Paraspirifer bownockeri), Silica Formation, Middle Devonian, northwestern Ohio (not a Michigan specimen)

FossilLower Peninsula

Pyritized fossils

Brassy, metallic fossils. Store them "inside rice or silica packets to keep it from rusting."

Details and 4 photos

Pyritized brachiopod (Paraspirifer bownockeri), Silica Formation, Middle Devonian, northwestern Ohio (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Pyritized brachiopod Paraspirifer, Silica Formation, Ohio (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Pyritized corals on a Paraspirifer brachiopod, Silica Formation, Ohio (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Pyritized ammonite, Charmouth Beach, England (not a Michigan specimen) Photo: Partonez, CC BY-SA 4.0

What it is: Fossils where pyrite replaced the original shell. EGLE on a Lake Huron find: "a pyrite concretion ... there may be a fossil - a crinoid calyx where the pyrite has replaced the original mineral."
Age: Not yet in our checked sources.
Where: EGLE: "Pyrite replacement in fossils is common in the Devonian shale in Sylvania, OH."
How to spot it: Brassy, metallic fossils. Store them "inside rice or silica packets to keep it from rusting."
Look-alikes: No look-alikes are published in our checked sources yet.

Sources: 10

Lepidodendron bark fossil, University of Michigan Museum of Natural History, Ann Arbor (where it was found is not stated, so it may not be a Michigan specimen)

FossilLower Peninsula

Coal-swamp plant fossils (Calamites, Lepidodendron, Stigmaria)

Lepidodendron bark has leaf scars in "a pattern that resembles the outer surface of a pineapple." Stigmaria is "covered in little dimples or depressions where smaller 'rootlets' emerged." Calamites shows vertical lines crossed by evenly spaced bands (nodes).

Details and 5 photos

Museum specimen Lepidodendron bark fossil, University of Michigan Museum of Natural History, Ann Arbor (where it was found is not stated, so it may not be a Michigan specimen) Photo: Daderot, Public domain
Lepidodendron bark scales, Stevenston Beach, Scotland (not a Michigan specimen) Photo: Rosser1954, CC BY-SA 4.0
Stigmaria, a Lepidodendron root, Stevenston Beach, Scotland (not a Michigan specimen) Photo: Rosser1954, CC BY-SA 4.0
Lepidodendron trunk with its scaly bark pattern, Kentucky, museum display (not a Michigan specimen) Photo: James St. John, CC BY 4.0
Calamites stem, Wrexham Museum, Wales, museum display (not a Michigan specimen) Photo: Rept0n1x, CC BY-SA 3.0

What it is: Fossils of coal-swamp plants. Lepidodendron was "a large, tree-like plant related to club mosses." Calamites were tree-like plants "closely related to modern horsetails." Stigmaria is the name for the "roots" of Lepidodendron and similar plants.
Age: U-M: "In Michigan, plant material is found in Pennsylvanian, late Carboniferous, aged rock" (323 to 298 million years ago).
Where: U-M: "localities in Jackson, Ingham, Eaton, Shiawassee, Saginaw, and Bay Counties being well-documented." No public collecting spot is named in our checked sources.
How to spot it: Lepidodendron bark has leaf scars in "a pattern that resembles the outer surface of a pineapple." Stigmaria is "covered in little dimples or depressions where smaller 'rootlets' emerged." Calamites shows vertical lines crossed by evenly spaced bands (nodes).
Look-alikes: U-M: Lepidodendron "is often mistaken for fossilized reptile or dinosaur scales."

At Grand Ledge, "collecting of fossils is not encouraged in Fitzgerald Park and ... access to the Clay Products Quarry is by permission only" (1987 field guide on the EGLE site). Private land needs the owner's permission. Rules change; check with the land manager; not legal advice.

Sources: 51 52

Holonema cf. farrowi armor plate, Presque Isle County, Michigan, Smithsonian National Museum of Natural History (USNM 23663; cropped to one of the two pieces)

FossilLower Peninsula

Devonian armored fish plates (placoderms)

U-M: placoderm plates "are found in consolidated rock, although that rock might be just a small loose cobble." Some plates carry small bumps (tubercles); one Rockport plate is told apart by "a lack of tubercles."

Details and 4 photos

Museum specimen Holonema cf. farrowi armor plate, Presque Isle County, Michigan, Smithsonian National Museum of Natural History (USNM 23663; cropped to one of the two pieces) Photo: Smithsonian National Museum of Natural History, CC0
Dunkleosteus head armor, a cast, Cleveland Shale, Ohio, museum display (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Holonema armor plate, Silica Formation, Paulding, Ohio, museum display (not a Michigan specimen) Photo: James St. John, CC BY 2.0
Arthrodire lower tooth plate, Silica Formation, Paulding, Ohio, museum display (not a Michigan specimen) Photo: James St. John, CC BY 2.0

What it is: Pieces of armor from placoderms, the armored fish. U-M: Michigan vertebrate fossils range from "fragments of the plates of prehistoric armored fish preserved in Devonian rocks" to mastodons and mammoths. A 2018 survey found "Nineteen genera of fishes" in Michigan's Middle and Late Devonian rocks, "of which thirteen are 'placoderms'."
Age: Devonian. The oldest Michigan finds are Eifelian (Middle Devonian), from the Dundee Limestone; others come from the Middle Devonian Traverse Group and the Late Devonian Antrim Shale.
Where: The Rockport Quarry Limestone has "the most diverse Devonian vertebrate fauna in Michigan." Its main fossil outcrop is the abandoned Kelly Island Limestone Quarry at Rockport State Park, Alpena County.
How to spot it: U-M: placoderm plates "are found in consolidated rock, although that rock might be just a small loose cobble." Some plates carry small bumps (tubercles); one Rockport plate is told apart by "a lack of tubercles."
Look-alikes: Modern bone. U-M: "it is much more common to find bones and teeth from modern animals than to find fossil bones." Michigan's Pleistocene bones lie in loose sediment, "not in rock like limestone or shale."

These are vertebrate fossils. The state 25 lb rule (R 299.922(hh)) covers only rocks, mineral specimens and invertebrate fossils, so it does not cover vertebrate fossils. Check with the DNR before keeping one from state land. If you are unsure, photograph it and leave it. National forests exclude vertebrate fossils. No collecting at Sleeping Bear Dunes, Pictured Rocks or Isle Royale (36 CFR 2.1). Rules change; not legal advice.

Sources: 53 54 40 17 14

Mastodon skeletons on display, University of Michigan Museum of Natural History (the male is a cast)

FossilLower Peninsula

Mastodon (state fossil) and mammoth

The Bristle Mammoth (Chelsea area, 2015) included "about 20 percent of the animal's bones, including the skull and two tusks," and "appears to be a hybrid between a woolly mammoth and a Columbian mammoth."

Details and 5 photos

Museum specimen Mastodon skeletons on display, University of Michigan Museum of Natural History (the male is a cast) Photo: WolfmanSF, CC BY-SA 4.0
Mastodon tooth, Mattapoisett River, Massachusetts, museum display (not a Michigan specimen) Photo: Daderot, CC0 1.0
Mastodon molar, Cleveland, Ohio, museum display (not a Michigan specimen) Photo: Tim Evanson, CC BY-SA 2.0
The Buesching mastodon skeleton, found in Indiana, museum display at the University of Michigan (not a Michigan specimen) Photo: Daderot, Public domain
Mastodon lower jaw, Shelton Mastodon site, Oakland County, museum display Photo: James St. John, CC BY 2.0

What it is: "The mastodon (Mammut americanum) is designated as the official fossil of this state." (2002 PA 162)
Age: U-M (2015): the animals were "disappearing about 11,700 years ago."
Where: U-M (2015): "the remains of about 300 mastodons and 30 mammoths have been recovered in Michigan." The State of Michigan says mastodon fossils have been found "in more than 250 locations." Most finds come from the southern half of the Lower Peninsula (Wilson 1967).
How to spot it: The Bristle Mammoth (Chelsea area, 2015) included "about 20 percent of the animal's bones, including the skull and two tusks," and "appears to be a hybrid between a woolly mammoth and a Columbian mammoth."
Look-alikes: No look-alikes are published in our checked sources yet.

Vertebrate fossils are excluded from casual collecting in national forests.

Sources: 2 55 3 56

Photo coming soon

Man-madeLower Peninsula

Leland Blue (slag glass)

Official sources describe only its color: "varying hues of blue" (Leelanau Historical Society).

Details

What it is: Man-made slag glass, not a natural rock (MGS: "Man-made materials like slag glass (e.g., Leland Blue)"). It is waste slag from the charcoal iron furnace that ran at Leland in the 1870s and 1880s. The Leelanau Historical Society calls the Blue Stones of Leland "remnants of the tons of slag from the smelting operation."
Age: Man-made, so it has no geologic age. It dates from Leland's iron-furnace years. The ironworks were built in 1870 (NPS; some local histories say 1872), and the Leland Lake Superior Iron Company and the firms that followed it ran the furnace until 1884 (NPS); the historical society lists a last firm from 1885.
Where: Lake Michigan beaches at Leland, Leelanau County. The historical society says rock-hounds who "comb the beach north of Leland" find it, and that "iron ore slag that washes ashore along Leland's beaches." The furnace stood north of the Leland River mouth, where the marina building and parking lot are now (NPS). Van's Beach, at the end of Cedar Street in Leland, is owned and managed by Leland Township. Township beaches are closed from one hour past sunset until sunrise.
How to spot it: Official sources describe only its color: "varying hues of blue" (Leelanau Historical Society).
Look-alikes: Look-alikes are not yet in our checked sources.

Leland Blue is man-made slag. Michigan's 25 lb yearly limit for state-owned land covers "any rock, mineral specimen (exclusive of any gold bearing material), or invertebrate fossil" (R 299.922(hh)) and does not mention slag. The Michigan Geological Survey says: "Man-made materials like slag glass (e.g., Leland Blue) are often not included in limits." That is guidance, not a rule. Van's Beach is a Leland Township beach. The township park ordinance has no rock or slag rule, but it says "Township property shall not be damaged or destroyed" and bans commercial sales unless the Township Board approves. Sleeping Bear Dunes National Lakeshore: no collecting (36 CFR 2.1); that rule bans removing rocks, minerals and cultural resources, and does not name slag. Last checked 2026-10-22. Rules change; check with the land manager; not legal advice.

Sources: 57 58 59 60 61 62 63 64 17 14 65

Full guides: Petoskey stone, Lake Superior agate, Where to hunt and collecting rules.

Sources (65)

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