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, 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.
