Borcarite is a rare borate mineral typically occurring as small, white to colorless tabular crystals or granular masses in skarn environments. It is primarily known from the Solongo borate deposit in Russia, where it forms in association with other borates and carbonates. Collectors prize it for its rarity and distinct chemical composition, though it is usually found as inconspicuous small crystalline masses.
Is this borcarite?
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 borcarite with a known reference. Borcarite sits at Mohs 4-4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous, slightly pearly on cleavages.
- 4Match the color rangeCompare against the expected color range: blue green, colorless, green, greenish blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, massive, granular aggregates.
Often confused with
Borcarite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside borcarite
Minerals reported to co-occur with borcarite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₄Mg(B₄O₆)(OH)₆(CO₃)₂
- Mohs hardness
- 4-4.5
- Density
- 2.77 g/cm³
- Streak
- White
- Luster
- Vitreous, slightly pearly on cleavages
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals, massive, granular aggregates
- Cleavage
- Perfect on {100}; perfect on {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In kotoite marbles, near the contact with granodiorite (Snezhnoye deposit, Russia); a rare secondary mineral probably formed by reaction of late hydrothermal fluids with brucite (Fuka, Japan)
Where rockhounds find borcarite
Classic worldwide localities
- Snezhnoye boron deposit, Izvestkovyi stream, Tas-Khayakhtakh Range, Polar Ural Mountains, and in the Solongo boron deposit, Buryatia, Siberia, Russia
- Fuka, near Bicchu, Okayama Prefecture, Japan
Field-hunting tip
Where it forms: In kotoite marbles, near the contact with granodiorite (Snezhnoye deposit, Russia); a rare secondary mineral probably formed by reaction of late hydrothermal fluids with brucite (Fuka, Japan). If you start seeing szaibélyite, uralborite, sibirskite in float, you are in the right ground. Typical habit: tabular crystals, massive, granular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify borcarite?+
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What rocks look like borcarite?+
What minerals are found with borcarite?+
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Find borcarite on the map
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