A pyritized gastropod is a fossil whose original shell material has been replaced or coated by pyrite in an anaerobic, iron-rich marine environment. Look for a brilliant, brassy metallic luster and well-defined internal whorls retaining the shape of the original mollusk. It is typically found in dark, organic-rich shale where oxygen levels were low during fossilization.
Is this pyritized gastropod?
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 gastropod with a known reference. Pyritized Gastropod 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 Gastropod leaves a greenish-black streak.
- 3Read the lusterHold the specimen under a strong light. Pyritized Gastropod 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 gastropod
Minerals reported to co-occur with pyritized gastropod. 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
Where rockhounds find pyritized gastropod
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 gastropod 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 gastropod photos
Common questions
How do you identify pyritized gastropod?+
Where is pyritized gastropod found?+
Can I find pyritized gastropod in the United States?+
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Find pyritized gastropod on the map
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