Rocks, minerals and fossils of Michigan

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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: 50 17 14

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

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

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

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

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

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

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