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. Birunite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Birunite typically shows a pearly luster.
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 earthy on Borax.

How to tell apart: Priceite is the harder of the two (Mohs 3-3.5 vs. 2); luster reads pearly on Birunite and earthy on Priceite.

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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

Look in evaporite deposits country, the host setting where birunite typically forms. If you start seeing borax, ulexite in float, you are in the right ground. Field specimens usually show a platy crystals, crusts, aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify birunite?+

Mohs hardness is 2. It typically shows a pearly luster. 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, Priceite. 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?+

Birunite typically forms in 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.