Birunite is a very rare hydrated calcium borate mineral known primarily from its type locality in Kazakhstan. It typically forms delicate, white platy or fibrous aggregates within evaporite settings, making it a highly sought-after rarity for specialized borate mineral collectors.
Is this birunite?
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 birunite with a known reference. Birunite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Birunite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Birunite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal 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.
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
- Ca₄B₁₀O₁₉·13H₂O
- Mohs hardness
- 2
- Density
- 2.1 g/cm³
- 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
- Typical price
- $50-200 per specimen
Where rockhounds find birunite
Classic worldwide localities
- Birun deposit, Kazakhstan
Field-hunting tip
Look in evaporite deposits country — that is 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
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Find birunite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
