Chaoite is an extremely rare polymorph of carbon first discovered in shock-metamorphosed graphite gneiss from an impact crater. It typically occurs as black microcrystalline inclusions within graphite and is distinguished from other carbon allotropes by its unique crystal structure resulting from high-pressure shock events.
Is this chaoite?
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 chaoite with a known reference. Chaoite sits at Mohs 1-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: submetallic.
- 4Match the color rangeCompare against the expected color range: dark gray.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: lamellar.
Often confused with
Chaoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Chaoite leaves white, Graphite leaves black to steel-gray, shining; luster reads submetallic on Chaoite and metallic; may be dull, earthy on Graphite.
How to tell apart: Diamond is the harder of the two (Mohs 10 vs. 1-2); streak differs, so Chaoite leaves white, Diamond leaves colorless; luster reads submetallic on Chaoite and adamantine to greasy on Diamond.
Often found alongside chaoite
Minerals reported to co-occur with chaoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- C
- Mohs hardness
- 1-2
- Density
- 3.33-3.43 g/cm³
- Colors
- Streak
- White
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Hexagonal
- Crystal habit
- Lamellar
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In shock-metamorphosed graphite gneisses and meteorites
Where rockhounds find chaoite
Classic worldwide localities
- Mottingen, in the Nördlinger Ries crater, Bavaria, Germany
Field-hunting tip
Where it forms: In shock-metamorphosed graphite gneisses and meteorites. If you start seeing graphite, zircon, rutile in float, you are in the right ground. Typical habit: lamellar. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify chaoite?+
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Find chaoite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
