Pyrite concretions, commonly known as pyrite suns, are flat, radiating crystalline growths that form between layers of shale. They are highly sought after by collectors for their unique disc-like shape and metallic brassy luster, often found by digging in the spoil piles of old coal mines.
Is this pyrite concretions?
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 pyrite concretions with a known reference. Pyrite Concretions sits at Mohs 6-6.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Pyrite Concretions leaves a greenish-black streak.
- 3Read the lusterHold the specimen under a strong light. Pyrite Concretions typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: brass-yellow.
- 5Look at form & habitCrystal system: cubic. Typical habit: radial fibrous disk.
Often confused with
Pyrite Concretions vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside pyrite concretions
Minerals reported to co-occur with pyrite concretions. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeS₂
- Mohs hardness
- 6-6.5
- Density
- 4.8-5.1 g/cm³
- Colors
- Streak
- Greenish-black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Radial Fibrous Disk
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Decorative
- Host rock
- Sedimentary Shale and Coal Beds
- Typical price
- $10-150 depending on size and radial definition
Where rockhounds find pyrite concretions
3 mapped spotsClassic worldwide localities
- Sparta, Illinois
- Carbondale, Illinois
- Coal mines of the Illinois Basin
Field-hunting tip
Look in sedimentary shale and coal beds country, the host setting where pyrite concretions typically forms. If you start seeing shale, coal, sphalerite in float, you are in the right ground. Field specimens usually show a radial fibrous disk habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Kansas, Vermont, West Virginia. Start trip planning there.
More pyrite concretions photos
Common questions
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Find pyrite concretions on the map
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