Copiapite is a secondary sulfate mineral commonly found as a bright yellow efflorescence in the oxidized zones of pyrite-rich ore deposits. Collectors primarily find it as thin crusts, aggregates of small platy crystals, or powdery masses associated with other secondary iron sulfates.
Is this copiapite?
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 copiapite with a known reference. Copiapite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly on {010}.
- 4Match the color rangeCompare against the expected color range: yellow, green, green yellow, yellow green, golden yellow.
- 5Look at form & habitCrystal system: triclinic. Typical habit: encrustations, massive, scaly.
Often confused with
Copiapite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads pearly on {010} on Copiapite and subadamantine to vitreous, resinous on fractures on Jarosite.
How to tell apart: Streak differs, so Copiapite leaves pale yellow, Coquimbite leaves white; luster reads pearly on {010} on Copiapite and vitreous on Coquimbite.
Often found alongside copiapite
Minerals reported to co-occur with copiapite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe²⁺Fe³⁺₄(SO₄)₆(OH)₂·20H₂O
- Mohs hardness
- 2.5-3
- Density
- 2.04-2.17 g/cm³
- Streak
- Pale yellow
- Luster
- Pearly on {010}
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
- Crystal habit
- Encrustations, massive, scaly
- Cleavage
- On {010}, perfect; on {101}, imperfect
- Rarity
- Common
- Uses
- Collector, Scientific study
- Host rock
- A secondary mineral formed typically by the weathering and oxidation of pyrite in a wide range of rock types, preserved in arid climates; rarely associated with fumarolic action
Where rockhounds find copiapite
1 mapped spotsClassic worldwide localities
- Coso Hot Springs, Inyo Co., Sulphur Bank, Lake Co., the Alma mine, Leona Heights, Alameda Co., California, USA
- Comstock Lode, Virginia City, Storey Co., Nevada, USA
- Dexter No. 7 mine, Calf Mesa, San Rafael district, Emery Co., Utah, USA
- Bisbee, Cochise Co., and from the United Verde mine, Jerome, Yavapai Co., Arizona, USA
- Tierra Amarilla, southeast of Copiapó, Atacama, Chile
- Alcaparrosa, near Cerritos Bayos, southwest of Calama, and at Chuquicamata, Antofagasta, Chile
Field-hunting tip
Where it forms: A secondary mineral formed typically by the weathering and oxidation of pyrite in a wide range of rock types, preserved in arid climates; rarely associated with fumarolic action. If you start seeing melanterite, alunogen, fibroferrite in float, you are in the right ground. Typical habit: encrustations, massive, scaly. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Missouri. Start trip planning there.
Common questions
How do you identify copiapite?+
Where is copiapite found?+
Can I find copiapite in the United States?+
What rocks look like copiapite?+
What minerals are found with copiapite?+
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Find copiapite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
