Ameghinite is a rare sodium borate mineral found almost exclusively in the evaporite deposits of Argentina. It typically forms colorless to white tabular crystals or massive aggregates within borate-rich lacustrine settings. Collectors prioritize specimens from the Tincalayu mine, where it is often associated with other borate species.
Is this ameghinite?
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 ameghinite with a known reference. Ameghinite 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. Ameghinite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Ameghinite 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, massive, granular.
Often confused with
Ameghinite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside ameghinite
Minerals reported to co-occur with ameghinite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaB₃O₃(OH)₄
- Mohs hardness
- 3.5
- Density
- 2.13 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Massive, Granular
- Cleavage
- Perfect On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Evaporite Deposits in Lacustrine Basins
- Typical price
- $50-300 per specimen
Where rockhounds find ameghinite
Classic worldwide localities
- Tincalayu Mine, Salta, Argentina
Field-hunting tip
Look in evaporite deposits in lacustrine basins country — that is the host setting where ameghinite typically forms. If you start seeing borax, ezcurrite, kernite in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ameghinite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
