Tincalconite is a common dehydration product of borax, often forming as a white, powdery coating on borax crystals exposed to air. It is most frequently found as pseudomorphs replacing the original borax crystals while retaining their shape. Collectors typically find it in arid salt lake deposits alongside other borate minerals.
Is this tincalconite?
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 tincalconite with a known reference. Tincalconite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Tincalconite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Tincalconite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray.
- 5Look at form & habitCrystal system: trigonal. Typical habit: pseudomorphs after borax, massive, powdery, earthy aggregates.
Often confused with
Tincalconite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside tincalconite
Minerals reported to co-occur with tincalconite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂B₄O₇·5H₂O
- Mohs hardness
- 2
- Density
- 1.88 g/cm³
- Streak
- White
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Pseudomorphs After Borax, Massive, Powdery, Earthy Aggregates
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Scientific Research
- Host rock
- Evaporite Deposits in Arid Salt Lakes
- Typical price
- $5-30 for micro or thumbnail specimens
Where rockhounds find tincalconite
Classic worldwide localities
- Searles Lake, California, USA
- Borax Lake, California, USA
- Kramers, California, USA
- Sijes, Argentina
Field-hunting tip
Look in evaporite deposits in arid salt lakes country — that is the host setting where tincalconite typically forms. If you start seeing borax, kernite, halite in float, you are in the right ground. Field specimens usually show a pseudomorphs after borax, massive, powdery, earthy aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find tincalconite on the map
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