Pinnoite is a rare borate mineral typically found in marine evaporite deposits as small, yellow, prismatic crystals or fibrous masses. Collectors look for its characteristic radial habits often embedded in halite or associated with other borate species like boracite.
Is this pinnoite?
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 pinnoite with a known reference. Pinnoite 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. Pinnoite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Pinnoite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellowish-brown, white.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: prismatic crystals, radial aggregates.
Often confused with
Pinnoite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside pinnoite
Minerals reported to co-occur with pinnoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgB₂O₄·3H₂O
- Mohs hardness
- 3.5
- Density
- 2.29 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Prismatic Crystals, Radial Aggregates
- Cleavage
- Distinct On {110}
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Evaporite Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find pinnoite
Classic worldwide localities
- Stassfurt, Germany
- Sperenberg, Germany
- Inder Deposit, Kazakhstan
Field-hunting tip
Look in evaporite deposits country — that is the host setting where pinnoite typically forms. If you start seeing boracite, halite, anhydrite 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 pinnoite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
