Boralsilite is an exceptionally rare borosilicate mineral typically found as tiny, colorless prismatic crystals. It was originally discovered in ejected limestone blocks within volcanic tuff, making it a highly sought-after specimen for advanced mineral collectors focusing on rare species.
Is this boralsilite?
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 boralsilite with a known reference. Boralsilite sits at Mohs 7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Boralsilite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Boralsilite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic crystals, radial aggregates.
Often confused with
Boralsilite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside boralsilite
Minerals reported to co-occur with boralsilite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₁₆B₆Si₂O₃₇
- Mohs hardness
- 7
- Density
- 3.37 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic Crystals, Radial Aggregates
- Cleavage
- None Observed
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Limestone Xenoliths
- Typical price
- $100-500 for small micros
Where rockhounds find boralsilite
Classic worldwide localities
- Capo di Bove, Rome, Italy
Field-hunting tip
Look in metamorphosed limestone xenoliths country, the host setting where boralsilite typically forms. If you start seeing sillimanite, corundum, spinel in float, you are in the right ground. Field specimens usually show a prismatic crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find boralsilite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
