Pyritized gastropods are fossils where the original shell material has been replaced or coated by pyrite in an anaerobic, iron-rich marine environment. Collectors should look for a brilliant, brassy metallic luster and well-defined internal whorls that retain the shape of the original mollusk. They are typically found in dark, organic-rich shales where oxygen levels were low during fossilization.
Is this pyritized gastropods?
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 pyritized gastropods with a known reference. Pyritized Gastropods sits at Mohs 3.5-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Pyritized Gastropods leaves a greenish-black streak.
- 3Read the lusterHold the specimen under a strong light. Pyritized Gastropods typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: brass yellow, gold, brown.
- 5Look at form & habitCrystal system: cubic. Typical habit: pseudomorphs after organic shell structures.
Often found alongside pyritized gastropods
Minerals reported to co-occur with pyritized gastropods. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeS₂
- Mohs hardness
- 3.5-4
- Density
- 4.8-5.1 g/cm³
- Colors
- Streak
- Greenish-black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Pseudomorphs After Organic Shell Structures
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Lapidary
- Host rock
- Sedimentary Shale and Clay Beds
- Typical price
- $10-200 per specimen
Where rockhounds find pyritized gastropods
1 mapped spotsClassic worldwide localities
- France
- Germany
- United Kingdom
- Russia
- USA
Field-hunting tip
Look in sedimentary shale and clay beds country, the host setting where pyritized gastropods typically forms. If you start seeing pyrite, calcite, shale in float, you are in the right ground. Field specimens usually show a pseudomorphs after organic shell structures habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Illinois. Start trip planning there.
More pyritized gastropods photos
Common questions
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Find pyritized gastropods on the map
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