Chalcocite is a major copper ore mineral often found in secondary enrichment zones of copper deposits. It is easily recognized by its dark lead-gray color, which frequently develops a dull or iridescent blue-purple tarnish upon exposure to air.
Is this chalcocite?
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 chalcocite with a known reference. Chalcocite 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. Chalcocite leaves a lead-gray to black streak.
- 3Read the lusterHold the specimen under a strong light. Chalcocite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: lead-gray, black, tarnish-blue, tarnish-iridescent.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, massive, granular, disseminated.
Often confused with
Chalcocite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Chalcocite leaves lead-gray to black, Bornite leaves greyish black.
How to tell apart: Streak differs — Chalcocite leaves lead-gray to black, Galena leaves lead-gray.
How to tell apart: Streak differs — Chalcocite leaves lead-gray to black, Covellite leaves lead gray to black.
Often found alongside chalcocite
Minerals reported to co-occur with chalcocite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₂S
- Mohs hardness
- 2.5-3
- Density
- 5.5-5.8 g/cm³
- Streak
- Lead-gray to Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Massive, Granular, Disseminated
- Cleavage
- Indistinct
- Rarity
- Common
- Uses
- Ore of Copper, Collector
- Host rock
- Hydrothermal Veins, Supergene Enrichment Zones in Copper Deposits
- Typical price
- $10-150 for thumbnail to cabinet sized specimens
Where rockhounds find chalcocite
33 mapped spotsClassic worldwide localities
- Bristol, Connecticut, USA
- Butte, Montana, USA
- Cornwall, England
- Tsumeb, Namibia
- Dzhezkazgan, Kazakhstan
U.S. states with chalcocite
Each link opens a state-specific list of mapped rockhounding spots that produce chalcocite.
Field-hunting tip
Look in hydrothermal veins, supergene enrichment zones in copper deposits country — that is the host setting where chalcocite typically forms. If you start seeing bornite, covellite, chalcopyrite in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, granular, disseminated habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah, New Mexico, Connecticut — start trip planning there.
Common questions
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Find chalcocite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
