Covellite is a striking copper sulfide mineral easily recognized by its deep indigo blue color and frequent iridescent tarnish. It is very soft and sectile, often forming platy or micaceous aggregates that can be scratched with a fingernail.
Is this covellite?
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 covellite with a known reference. Covellite sits at Mohs 1.5-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: lead-gray, shining.
- 3Read the lusterHold the specimen under a strong light. Luster: submetallic, inclining to resinous, somewhat pearly on cleavage; subresinous to dull when massive.
- 4Match the color rangeCompare against the expected color range: indigo blue, iridescent, light blue, dark blue, black.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: foliated, platy.
Often confused with
Covellite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Covellite leaves lead-gray, shining, Chalcocite leaves blackish lead-gray; luster reads submetallic, inclining to resinous, somewhat pearly on cleavage; subresinous to dull when massive on Covellite and metallic on Chalcocite.
How to tell apart: Bornite is the harder of the two (Mohs 3-3.25 vs. 1.5-2); streak differs, so Covellite leaves lead-gray, shining, Bornite leaves pale grayish black; luster reads submetallic, inclining to resinous, somewhat pearly on cleavage; subresinous to dull when massive on Covellite and metallic on Bornite.
How to tell apart: Streak differs, so Covellite leaves lead-gray, shining, Digenite leaves grayish black.
Often found alongside covellite
Minerals reported to co-occur with covellite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuS
- Mohs hardness
- 1.5-2
- Density
- 4.6-4.76 g/cm³
- Colors
- Streak
- Lead-gray, shining
- Luster
- Submetallic, inclining to resinous, somewhat pearly on cleavage; subresinous to dull when massive
- Transparency
- Opaque
- Crystal system
- Hexagonal
- Crystal habit
- Foliated, platy
- Cleavage
- Perfect on {0001}
- Rarity
- Common
- Uses
- Collector, Ore of copper
- Host rock
- Most commonly of secondary origin in the zone of oxidation in sulfide copper deposits
Where rockhounds find covellite
1 mapped spotsClassic worldwide localities
- Butte, Silver Bow Co., Montana, as primary ore, USA
- Kennicott, Alaska, USA
- Summitville, Rio Grande Co., Colorado, USA
- La Sal district, San Juan Co., Utah, USA
- Vesuvius, Campania (type locality) and as Calabona mine, Alghero, Sardinia, Italy
- Bor, Serbia
Field-hunting tip
Where it forms: Most commonly of secondary origin in the zone of oxidation in sulfide copper deposits. If you start seeing chalcopyrite, chalcocite, djurleite in float, you are in the right ground. Typical habit: foliated, platy. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Maryland. Start trip planning there.
Common questions
How do you identify covellite?+
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Find covellite on the map
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