Birunite is a rare calcium sulfate. It was approved as a distinct mineral species in 1957, from material found in Uzbekistan.

Hardness

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrare

Birunite

Birunite is a rare calcium sulfate. It was approved as a distinct mineral species in 1957, from material found in Uzbekistan.

Hardness: 2
Luster: Pearly
Streak: White
Transparency: Translucent

No image

Is this birunite?

5-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 birunite with a known reference. Birunite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: pearly.
4
Match the color range
Compare against the expected color range: white, colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: platy crystals, crusts, aggregates.

Often confused with

Birunite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Borax

Mohs 2-2.5

How to tell apart: Luster reads pearly on Birunite and vitreous to resinous, may be earthy on Borax.

How to tell apart: Colemanite is the harder of the two (Mohs 4.5 vs. 2); luster reads pearly on Birunite and vitreous to adamantine on Colemanite.

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Often found alongside birunite

Minerals reported to co-occur with birunite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Ca₁₈(SiO₃)₈.₅(CO₃)₈.₅(SO₄)·15H₂O
Mohs hardness: 2
Density: 2.1 g/cm³
Colors: White Colorless
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Platy crystals, crusts, aggregates
Cleavage: Perfect
Rarity: Rare
Uses: Collector
Host rock: evaporite deposits

Where rockhounds find birunite

Classic worldwide localities

Birun deposit, Kazakhstan

Field-hunting tip

Where it forms: evaporite deposits. If you start seeing borax, ulexite in float, you are in the right ground. Typical habit: platy crystals, crusts, aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify birunite?+

Mohs hardness is 2. Luster: pearly. The streak is white. Common colors include white, colorless.

Where is birunite found?+

Notable localities include Birun deposit, Kazakhstan.

What rocks look like birunite?+

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

What minerals are found with birunite?+

Birunite commonly co-occurs with borax, ulexite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does birunite form in?+

Where it forms: evaporite deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is birunite used for?+

Birunite is used in collector.

Find birunite on the map

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