Ferricopiapite is a secondary sulfate mineral that typically forms as yellow, earthy to crystalline crusts in the oxidation zones of sulfide-rich ore bodies. It is famously associated with the breakdown of pyrite and other iron-sulfide minerals in arid environments where evaporation leads to the precipitation of hydrated sulfates.
Is this ferricopiapite?
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 ferricopiapite with a known reference. Ferricopiapite sits at Mohs ~2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: light yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly.
- 4Match the color rangeCompare against the expected color range: yellow, orange.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy crystals, tabular, crusts, efflorescent aggregates.
Often confused with
Ferricopiapite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ferricopiapite leaves light yellow, Copiapite leaves pale yellow.
How to tell apart: Streak differs, so Ferricopiapite leaves light yellow, Jarosite leaves pale yellow; luster reads pearly on Ferricopiapite and subadamantine to vitreous, resinous on fractures on Jarosite.
How to tell apart: Streak differs, so Ferricopiapite leaves light yellow, Melanterite leaves white; luster reads pearly on Ferricopiapite and vitreous on Melanterite.
Often found alongside ferricopiapite
Minerals reported to co-occur with ferricopiapite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe³⁺₄(SO₄)₆(OH)₂·20H₂O
- Mohs hardness
- ~2
- Density
- 2.14 g/cm³
- Streak
- Light yellow
- Luster
- Pearly
- Transparency
- Semitransparent
- Crystal system
- Triclinic
- Crystal habit
- Platy crystals, tabular, crusts, efflorescent aggregates
- Cleavage
- On {010}, perfect
- Rarity
- Common
- Uses
- Collector
- Host rock
- A secondary mineral formed typically by the weathering and oxidation of iron sulfide in a wide range of rock types, preserved in arid climates
Where rockhounds find ferricopiapite
Classic worldwide localities
- Campbell mine, Bisbee, Cochise Co., Arizona, USA
- Coso Hot Springs, Inyo Co., California, USA
- Dexter No. 7 mine, Calf Mesa, San Rafael district, Emery Co., Utah, USA
- Atacama, at Tierra Amarilla, southeast of Copiapó, Chile
- Antofagasta, from Alcaparrosa, near Cerritos Bayos and in the Sierra Gorda district, both southwest of Calama, Chile
- Capillitas mine, Catamarca Province, Argentina
Field-hunting tip
Where it forms: A secondary mineral formed typically by the weathering and oxidation of iron sulfide in a wide range of rock types, preserved in arid climates. If you start seeing pyrite in float, you are in the right ground. Typical habit: platy crystals, tabular, crusts, efflorescent aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferricopiapite?+
Where is ferricopiapite found?+
What rocks look like ferricopiapite?+
What minerals are found with ferricopiapite?+
What kind of rock does ferricopiapite form in?+
What is ferricopiapite used for?+
Find ferricopiapite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
