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, so 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, so 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, 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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