Coquimbite is a rare hydrated iron sulfate mineral typically found as a secondary mineral in the oxidized zones of pyrite-bearing deposits. It is best identified by its delicate pale violet to white prismatic crystals, though it is highly soluble and must be kept in a dry environment to prevent dehydration and breakdown.
Is this coquimbite?
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 coquimbite with a known reference. Coquimbite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Coquimbite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Coquimbite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: violet, pale violet, white, yellowish, greenish.
- 5Look at form & habitCrystal system: trigonal. Typical habit: hexagonal prisms, granular, massive.
Often confused with
Coquimbite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Coquimbite leaves white, Copiapite leaves yellow; luster reads vitreous on Coquimbite and pearly on Copiapite.
How to tell apart: Streak differs — Coquimbite leaves white, Jarosite leaves yellow.
Often found alongside coquimbite
Minerals reported to co-occur with coquimbite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₂(SO₄)₃·9H₂O
- Mohs hardness
- 2.5
- Density
- 2.1 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Hexagonal Prisms, Granular, Massive
- Cleavage
- Distinct On {10-10}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Oxidized Zones of Sulfide Ore Deposits
- Typical price
- $10-60 thumbnail, $50-200 cabinet
Where rockhounds find coquimbite
Classic worldwide localities
- Coquimbo, Chile
- Chuquicamata, Chile
- Alcaparrosa Mine, Chile
- Rio Tinto, Spain
- Iron Mountain, California, USA
Field-hunting tip
Look in oxidized zones of sulfide ore deposits country — that is the host setting where coquimbite typically forms. If you start seeing copiapite, jarosite, amarantite in float, you are in the right ground. Field specimens usually show a hexagonal prisms, granular, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find coquimbite on the map
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