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.

Hardness

Mohs

Luster

Metallic

Transparency

Opaque

mineralrare

Decagonite

Hardness: 6
Luster: Metallic
Transparency: Opaque

No image

Is this decagonite?

4-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch decagonite with a known reference. Decagonite sits at Mohs 6, softer than the next harder reference, harder than the previous one.
2
Read the luster
Hold the specimen under a strong light. Luster: metallic.
3
Match the color range
Compare against the expected color range: gray, black.
4
Look at form & habit
Crystal system: decagonal. 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: Decagonite is noticeably harder (Mohs 6 vs. 3.5-4).

Compare →

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: Al₇₁Ni₂₄Fe₅
Mohs hardness: 6
Density: 6.05 g/cm³
Colors: Gray Black
Luster: Metallic
Transparency: Opaque
Crystal system: Decagonal
Crystal habit: Anhedral grains
Rarity: Rare
Uses: Collector
Host rock: From impact shock metamorphism in a CV3 carbonaceous chondrite meteorite

Where rockhounds find decagonite

Classic worldwide localities

Khatyrka meteorite
Chukotka Autonomous Okrug, Russia

Field-hunting tip

Where it forms: From impact shock metamorphism in a CV3 carbonaceous chondrite meteorite. If you start seeing al-bearing trevorite, diopside, forsterite in float, you are in the right ground. Typical habit: anhedral grains. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify decagonite?+

Mohs hardness is 6. Luster: metallic. Common colors include gray, black.

Where is decagonite found?+

Notable localities include Khatyrka meteorite; Chukotka Autonomous Okrug, Russia.

Is decagonite safe to handle?+

Decagonite contains nickel. Wash your hands afterwards, never grind or breathe the dust, and store it apart from specimens you handle often.

What rocks look like decagonite?+

Decagonite is most often confused with Pyrite, Pentlandite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with decagonite?+

Decagonite commonly co-occurs with Al-bearing trevorite, Diopside, Forsterite, Ahrensite, Clinoenstatite, Nepheline. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does decagonite form in?+

Where it forms: From impact shock metamorphism in a CV3 carbonaceous chondrite meteorite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is decagonite used for?+

Decagonite is used in collector.

Find decagonite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.