Antofagastaite is a rare hydrated sodium-calcium sulfate mineral typically found as delicate, needle-like or fibrous crystal aggregates in arid evaporite settings. Collectors look for these fragile formations within the hyper-arid regions of the Atacama Desert in Chile, where it occurs as a secondary precipitate.
Is this antofagastaite?
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 antofagastaite with a known reference. Antofagastaite 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. Antofagastaite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Antofagastaite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, acicular, prismatic.
Often confused with
Antofagastaite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside antofagastaite
Minerals reported to co-occur with antofagastaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂Ca(SO₄)₂·2H₂O
- Mohs hardness
- 2
- Density
- 2.19 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, Acicular, Prismatic
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Evaporite Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find antofagastaite
Classic worldwide localities
- Antofagasta, Chile
Field-hunting tip
Look in evaporite deposits country — that is the host setting where antofagastaite typically forms. If you start seeing halite, anhydrite, gypsum in float, you are in the right ground. Field specimens usually show a fibrous, acicular, prismatic habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify antofagastaite?+
Where is antofagastaite found?+
How much is antofagastaite worth?+
What rocks look like antofagastaite?+
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Find antofagastaite on the map
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