Coprolite
Coprolite is trace fossil (phosphatized/silicified dung), Calcium phosphate or silica replacement. In the hand, it rates 3 to 7 (phosphatic vs silicified) on the Mohs scale, and it runs brown-grey and tan with darker swirls. Novelty-priced; scientifically documented specimens are worth more.
The geology.
Coprolite carries the formula Calcium phosphate or silica replacement. It belongs to the none (fossil) system. On paper it is trace fossil (phosphatized/silicified dung).
It sits at 3 to 7 (phosphatic vs silicified) on the Mohs scale. The surface reads dull to waxy polished. Light behaviour is opaque. Specific gravity runs 2.4 to 3.0. The streak is white to brownish. It breaks with uneven to conchoidal fracture.
A suspiciously sculptural lump with rounded ropy or pinched contours, true coprolites show phosphatic composition, sometimes spiral structure, and may contain visible bone or scale fragments from the meal.
Expect to see it as rounded lumpy masses, spiral forms (shark), polished display halves or novelty gifts.
The origins.
Anywhere animals fossilized, Washington's Miocene beds, Utah's Morrison Formation (much debated), South Carolina phosphate beds (shark coprolites).
On value, the database notes: novelty-priced; scientifically documented specimens are worth more.
Traditional associations.
In energy work traditions, coprolite is offered with a wink as the ultimate transformation stone, proof anything can become beautiful with enough time.
Recorded here because it is part of how this material is sold, not because it is a property of the material.
Spotting the real thing.
A suspiciously sculptural lump with rounded ropy or pinched contours, true coprolites show phosphatic composition, sometimes spiral structure, and may contain visible bone or scale fragments from the meal.
The trade's open secret: most polished rainbow 'dinosaur coprolite' is plain agatized rock with a fun story, genuine identifiable coprolites usually look like, well, what they are.
| Looks like | How to tell them apart |
|---|---|
| Ordinary concretions | Concretions are the great pretender, uniform mineral inside, no phosphate chemistry, no food inclusions |
| Mud pebbles | No internal structure or inclusions at all |
| Agate nodules (Utah 'dino poop') | Much polished 'dinosaur coprolite' is actually just colorful jasper-agate, buyers beware, honest dealers note it |
At-home tests.
None of these need a lab. A 10x loupe, good daylight and a steady hand cover most of what a buyer needs to know about coprolite.
| Test | What you should see |
|---|---|
| Under a loupe | Loupe for fish scales, bone bits, or plant fragments inside |
| By weight | Phosphatic types feel dense; geologists confirm with chemistry |
| By eye | Spiral form suggests shark or primitive fish origin |
If these checks leave you unsure, that is what appraisers are for. Do not file, heat or soak a piece to find out.
Care & handling.
At 3 to 7 (phosphatic vs silicified) on the Mohs scale this is a soft material. Keep it as a display piece, store it apart from harder stones, and skip daily-wear settings.
It breaks with uneven to conchoidal fracture, which is worth knowing before you set it or drop it.
Most damage happens during cleaning, not wearing. Avoid steamers, ultrasonic tanks and anything from under the sink.
A deeper look.
Extended detail on composition, sourcing, authentication and market value.
The physical record
The formula on record is Calcium phosphate or silica replacement. Crystal system: None (fossil). Specific gravity: 2.4 to 3.0. Streak: White to brownish. Cleavage and fracture: Uneven to conchoidal fracture.
How it reaches the market
Anywhere animals fossilized, Washington's Miocene beds, Utah's Morrison Formation (much debated), South Carolina phosphate beds (shark coprolites).
What it gets confused with
Ordinary concretions: Concretions are the great pretender, uniform mineral inside, no phosphate chemistry, no food inclusions. Mud pebbles: No internal structure or inclusions at all. Agate nodules (Utah 'dino poop'): Much polished 'dinosaur coprolite' is actually just colorful jasper-agate, buyers beware, honest dealers note it.
What it is worth
Novelty-priced; scientifically documented specimens are worth more.
Where buyers get caught
The trade's open secret: most polished rainbow 'dinosaur coprolite' is plain agatized rock with a fun story, genuine identifiable coprolites usually look like, well, what they are.
One more thing
The Victorian scientist William Buckland coined 'coprolite' in 1829 after realizing the 'bezoar stones' in Lyme Regis cliffs were ichthyosaur droppings, his student Mary Anning had been finding them inside skeletons all along.
An education-first guide.
There is nothing to buy on this page. Coprolite is not part of our catalogue, and the guide is here anyway because somebody searching the name deserves a straight answer.
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