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, so Coquimbite leaves white, Copiapite leaves yellow; luster reads vitreous on Coquimbite and pearly on Copiapite.
How to tell apart: Streak differs, so 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, 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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