Tunellite is a rare strontium borate mineral that typically forms as delicate, transparent, tabular crystals or radiating clusters. It is primarily found in California borate deposits, often associated with other rare borate species in evaporite sequences.
Is this tunellite?
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 tunellite with a known reference. Tunellite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Tunellite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Tunellite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, platy.
Often confused with
Tunellite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside tunellite
Minerals reported to co-occur with tunellite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SrB₆O₁₀·4H₂O
- Mohs hardness
- 3.5
- Density
- 2.42 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Platy
- Cleavage
- Perfect On {010}
- Fluorescence
- White Under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Borate Deposits in Sedimentary Environments
- Typical price
- $20-150 for thumbnail to small cabinet specimens
Where rockhounds find tunellite
Classic worldwide localities
- Boron District, California, USA
- Tick Canyon, California, USA
Field-hunting tip
Look in borate deposits in sedimentary environments country — that is the host setting where tunellite typically forms. If you start seeing colemanite, meyerhofferite, veatchite in float, you are in the right ground. Field specimens usually show a tabular crystals, platy habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find tunellite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
