Trembathite is a rare borate mineral that belongs to the boracite group, typically occurring in evaporite deposits. It often forms pseudo-cubic crystals that are visually indistinguishable from boracite without specialized X-ray diffraction or chemical analysis.
Is this trembathite?
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 trembathite with a known reference. Trembathite sits at Mohs 6-8, 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.
- 4Match the color rangeCompare against the expected color range: colorless, light blue.
- 5Look at form & habitCrystal system: trigonal. Typical habit: pseudo-cubic crystals, granular, massive.
Often confused with
Trembathite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside trembathite
Minerals reported to co-occur with trembathite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₃B₇O₁₃Cl
- Mohs hardness
- 6-8
- Density
- 2.84-3.34 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Pseudo-cubic crystals, granular, massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare component of marine evaporite borate deposits
Where rockhounds find trembathite
Classic worldwide localities
- Salt Springs evaporite deposit, and in the Potash Corporation of America mine, Penobsquis evaporite deposit, near Sussex, New Brunswick, Canada
- Boulby potash mine, northwest of Whitby, Yorkshire, England
Field-hunting tip
Where it forms: A rare component of marine evaporite borate deposits. If you start seeing halite, hilgardite in float, you are in the right ground. Typical habit: pseudo-cubic crystals, granular, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify trembathite?+
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What rocks look like trembathite?+
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Find trembathite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
