Decagonite is a remarkable naturally occurring quasicrystal that exhibits forbidden icosahedral symmetry. It is found exclusively as microscopic inclusions within the Khatyrka meteorite and is characterized by its unique aluminum-nickel-iron composition.
Is this decagonite?
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 decagonite with a known reference. Decagonite sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Decagonite leaves a gray streak.
- 3Read the lusterHold the specimen under a strong light. Decagonite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: silver, metallic gray.
- 5Look at form & habitCrystal system: icosahedral. Typical habit: anhedral grains.
Often confused with
Decagonite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Decagonite leaves gray, Pyrite leaves greenish-black to brownish-black.
How to tell apart: Decagonite is noticeably harder (Mohs 6 vs. 3.5-4); streak differs — Decagonite leaves gray, Pentlandite leaves light bronze-brown.
Often found alongside decagonite
Minerals reported to co-occur with decagonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₇₁Ni₂₄Fe₄
- Mohs hardness
- 6
- Density
- 6.05 g/cm³
- Colors
- Streak
- Gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Icosahedral
- Crystal habit
- Anhedral Grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- CV3 Carbonaceous Chondrite Meteorites
- Typical price
- n/a (extremely rare meteorite inclusion)
Where rockhounds find decagonite
Classic worldwide localities
- Khatyrka meteorite
- Chukotka Autonomous Okrug, Russia
Field-hunting tip
Look in cv3 carbonaceous chondrite meteorites country — that is the host setting where decagonite typically forms. If you start seeing stishovite, spinel, diopside in float, you are in the right ground. Field specimens usually show a anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find decagonite on the map
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