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. Streak: pale green to bluish green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to subadamantine, pearly on {0001}.
- 4Match the color rangeCompare against the expected color range: emerald green, bluish green, grass green.
- 5Look at form & habitCrystal system: trigonal. Typical habit: massive, platy, tabular.
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).
How to tell apart: Olivenite is the harder of the two (Mohs 3 vs. 2); streak differs, so Chalcophyllite leaves pale green to bluish green, Olivenite leaves olive-green to brown; luster reads vitreous to subadamantine, pearly on {0001} on Chalcophyllite and adamantine to vitreous, pearly to silky if fibrous on Olivenite.
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
- Cu₁₈Al₂(AsO₄)₄(SO₄)₃(OH)₂₄·36H₂O
- Mohs hardness
- 2
- Density
- 2.67-2.69 g/cm³
- Streak
- Pale green to bluish green
- Luster
- Vitreous to subadamantine, pearly on {0001}
- Transparency
- Transparent to translucent
- Crystal system
- Trigonal
- Crystal habit
- Massive, platy, tabular
- Cleavage
- {0001}, perfect, micaceous; {1011}, in traces
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in the oxidized zone of some arsenic-bearing hydrothermal polymetallic deposits
Where rockhounds find chalcophyllite
Classic worldwide localities
- Calumet and Arizona mine, Bisbee, Cochise Co., USA
- Majuba Hill mine, Antelope district, Pershing Co., Nevada, USA
- Mammoth and Ajax mines, Tintic district, Juab Co., Utah, USA
- Virneberg mine, near Rheinbreitbach, Rhineland-Palatinate, Germany
- Clara mine, near Oberwolfach, Black Forest, Germany
- Schwaz, Tirol, Austria
Field-hunting tip
Where it forms: A rare secondary mineral in the oxidized zone of some arsenic-bearing hydrothermal polymetallic deposits. If you start seeing azurite, malachite, brochantite in float, you are in the right ground. Typical habit: massive, platy, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify chalcophyllite?+
Where is chalcophyllite found?+
Is chalcophyllite safe to handle?+
What rocks look like chalcophyllite?+
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Find chalcophyllite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
