Torrecillasite is a rare arsenic-bearing mineral found in hyper-arid saline environments. It typically appears as yellow crusts or small aggregates within evaporite deposits in the Atacama region of Chile.
Is this torrecillasite?
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 torrecillasite with a known reference. Torrecillasite sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Torrecillasite leaves a pale yellow streak.
- 3Read the lusterHold the specimen under a strong light. Torrecillasite typically shows a resinous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: microcrystalline aggregates.
Often confused with
Torrecillasite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Torrecillasite leaves pale yellow, Claudetite leaves white; luster reads resinous on Torrecillasite and vitreous on Claudetite.
How to tell apart: Torrecillasite is noticeably harder (Mohs 3 vs. 1.5); streak differs — Torrecillasite leaves pale yellow, Arsenolite leaves white; luster reads resinous on Torrecillasite and vitreous on Arsenolite.
Often found alongside torrecillasite
Minerals reported to co-occur with torrecillasite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaAs₄O₆Cl
- Mohs hardness
- 3
- Density
- 4.56 g/cm³
- Colors
- Streak
- Pale Yellow
- Luster
- Resinous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Microcrystalline Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Evaporite Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find torrecillasite
Classic worldwide localities
- Torrecillas mine, Salar de Grande, Chile
Field-hunting tip
Look in evaporite deposits country — that is the host setting where torrecillasite typically forms. If you start seeing halite, gypsum, amarantite in float, you are in the right ground. Field specimens usually show a microcrystalline aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find torrecillasite on the map
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