Chalcophyllite is a rare copper-arsenic sulfate mineral prized by collectors for its brilliant, emerald-green tabular crystals. It typically forms in the oxidation zones of hydrothermal copper deposits where it is often found as fragile, leaf-like or foliated clusters.
Is this chalcophyllite?
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 chalcophyllite with a known reference. Chalcophyllite 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. Chalcophyllite leaves a pale green streak.
- 3Read the lusterHold the specimen under a strong light. Chalcophyllite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: emerald-green, grass-green, blue-green.
- 5Look at form & habitCrystal system: trigonal. Typical habit: tabular, hexagonal-shaped crystals, foliated masses.
Often confused with
Chalcophyllite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Mixite is the harder of the two (Mohs 3-4 vs. 2); streak differs — Chalcophyllite leaves pale green, Mixite leaves white.
How to tell apart: Olivenite is the harder of the two (Mohs 3 vs. 2); streak differs — Chalcophyllite leaves pale green, Olivenite leaves olive-green; luster reads vitreous on Chalcophyllite and adamantine on Olivenite.
How to tell apart: Luster reads vitreous on Chalcophyllite and pearly on Tyrolite.
Often found alongside chalcophyllite
Minerals reported to co-occur with chalcophyllite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₁₈Al₂As₃(SO₄)₂(OH)₂₇·36H₂O
- Mohs hardness
- 2
- Density
- 2.6-2.7 g/cm³
- Streak
- Pale Green
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Tabular, Hexagonal-shaped Crystals, Foliated Masses
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Copper-arsenic Deposits
- Typical price
- $20-200 thumbnail
Where rockhounds find chalcophyllite
Classic worldwide localities
- Cornwall (UK)
- Majuba Hill (USA)
- Schmiedeberg (Germany)
- Copiapo (Chile)
Field-hunting tip
Look in oxidized zones of copper-arsenic deposits country — that is the host setting where chalcophyllite typically forms. If you start seeing azurite, malachite, olivenite in float, you are in the right ground. Field specimens usually show a tabular, hexagonal-shaped crystals, foliated masses habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find chalcophyllite on the map
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