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, so Chalcocite leaves lead-gray to black, Bornite leaves greyish black.
How to tell apart: Streak differs, so Chalcocite leaves lead-gray to black, Galena leaves lead-gray.
How to tell apart: Streak differs, so 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, 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.
