Biringuccite is a rare borate mineral typically found as white, platy, or micaceous aggregates in geothermal or evaporite environments. It is often identified by its association with other borate species and its specific paragenesis in fumarolic areas, though it is quite difficult to distinguish macroscopically from similar borates without XRD analysis.
Is this biringuccite?
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 biringuccite with a known reference. Biringuccite sits at Mohs 2.5, 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: pearly.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, aggregates, crusts.
Often confused with
Biringuccite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads pearly on Biringuccite and vitreous to resinous, may be earthy on Borax.
How to tell apart: Luster reads pearly on Biringuccite and vitreous; silky or satiny in fibrous aggregates on Ulexite.
How to tell apart: Probertite is the harder of the two (Mohs 3.5 vs. 2.5); luster reads pearly on Biringuccite and vitreous, may be satiny on Probertite.
Often found alongside biringuccite
Minerals reported to co-occur with biringuccite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂B₅O₈(OH)·H₂O
- Mohs hardness
- 2.5
- Density
- 2.32 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Platy crystals, aggregates, crusts
- Cleavage
- Good on {001}; good on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As scales on piping in a geothermal field
Where rockhounds find biringuccite
Classic worldwide localities
- Larderello, Val di Cecina, Tuscany, Italy
Field-hunting tip
Where it forms: As scales on piping in a geothermal field. If you start seeing nasinite, thénardite, orpiment in float, you are in the right ground. Typical habit: platy crystals, aggregates, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
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Find biringuccite on the map
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