A fossil is the preserved remains, impression, or trace of ancient life found in sedimentary rock. It often undergoes mineralization, with the original material replaced by silica, calcite, or pyrite, producing a detailed replica of the original biological structure.
Is this fossil?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch fossil with a known reference. Fossil sits at Mohs 3-7, softer than the next harder reference, harder than the previous one.
- 2Name the organismDecide what left the fossil before worrying about the rock. Organism: Any once-living thing.
- 3Check the preservationPreservation: Varies: permineralization, casts and molds, replacement and recrystallization, carbonization and other processes. That controls the weight, the hardness and how the piece takes a polish.
- 4Read the lusterHold the specimen under a strong light. Luster: dull to vitreous.
- 5Match the color rangeCompare against the expected color range: brown, gray, white, tan, black.
Often found alongside fossil
Minerals reported to co-occur with fossil. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Mohs hardness
- 3-7
- Density
- 2.0-3.0 g/cm³
- Luster
- Dull to vitreous
- Transparency
- Opaque
- Fluorescence
- Variable
- Rarity
- Common
- Uses
- Collector, Educational, Decorative, Lapidary
- Host rock
- sedimentary strata
- Organism
- Any once-living thing
- Preservation
- Varies: permineralization, casts and molds, replacement and recrystallization, carbonization and other processes
Where rockhounds find fossil
150 mapped spotsClassic worldwide localities
- Morocco
- USA (Wyoming)
- Germany
- China
- Madagascar
U.S. states with fossil
Each link opens a state-specific list of mapped rockhounding spots that produce fossil.
- Oregon25 spots
- Michigan13 spots
- Ohio12 spots
- Florida9 spots
- Maryland9 spots
- Nebraska8 spots
- Missouri7 spots
- New Jersey7 spots
Field-hunting tip
Where it forms: sedimentary strata. If you start seeing calcite, quartz, pyrite in float, you are in the right ground. In the U.S., the densest reported localities are in Oregon, Michigan, Ohio. Start trip planning there.
More fossil photos
Common questions
How do you identify fossil?+
Where is fossil found?+
Can I find fossil in the United States?+
What minerals are found with fossil?+
What kind of rock does fossil form in?+
What is fossil used for?+
Find fossil on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
