Alfredstelznerite is an extremely rare calcium borate mineral that forms as distinct prismatic crystals within evaporite environments. It is primarily known from its type locality in Argentina, where it is found associated with other borate minerals like ulexite and borax.
Is this alfredstelznerite?
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 alfredstelznerite with a known reference. Alfredstelznerite 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. Alfredstelznerite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Alfredstelznerite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: triclinic. Typical habit: prismatic crystals.
Often confused with
Alfredstelznerite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Alfredstelznerite is noticeably harder (Mohs 3.5 vs. 2-2.5); luster reads vitreous on Alfredstelznerite and vitreous to earthy on Borax.
How to tell apart: Alfredstelznerite is noticeably harder (Mohs 3.5 vs. 2.5); luster reads vitreous on Alfredstelznerite and silky on Ulexite.
Often found alongside alfredstelznerite
Minerals reported to co-occur with alfredstelznerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₄(SO₄)(OH)₆(B₁₈O₂₉(OH)₅)·20H₂O
- Mohs hardness
- 3.5
- Density
- 2.42 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Prismatic Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Evaporite Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find alfredstelznerite
Classic worldwide localities
- Sierra de Cacho, Argentina
Field-hunting tip
Look in evaporite deposits country — that is the host setting where alfredstelznerite typically forms. If you start seeing borax, ulexite, gypsum in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find alfredstelznerite on the map
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