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, 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?+
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Find birunite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
