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.
- 2Name the organismDecide what left the fossil before worrying about the rock. Organism: Snails (class Gastropoda). Age: Gastropods: Late Cambrian to recent.
- 3Check the preservationPreservation: Pyritized (replaced by pyrite). That controls the weight, the hardness and how the piece takes a polish.
- 4Read the lusterHold the specimen under a strong light. Luster: metallic.
- 5Match the color rangeCompare against the expected color range: brass yellow, gold, brown.
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
- Mohs hardness
- 3.5-4
- Density
- 4.8-5.1 g/cm³
- Colors
- Luster
- Metallic
- Transparency
- Opaque
- Rarity
- Uncommon
- Uses
- Collector, Lapidary
- Host rock
- sedimentary shale and clay beds
- Organism
- Snails (class Gastropoda)
- Age
- Gastropods: Late Cambrian to recent
- Preservation
- Pyritized (replaced by pyrite)
Where rockhounds find pyritized gastropod
1 mapped spotsClassic worldwide localities
- France
- Germany
- United Kingdom
- Russia
- USA
Field-hunting tip
Where it forms: sedimentary shale and clay beds. If you start seeing pyrite, calcite, shale in float, you are in the right ground. 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?+
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Find pyritized gastropod on the map
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