A copper nugget is a mass of native copper, a metallic element with a distinct copper-red color and high density. It occurs in massive, dendritic, or arborescent form, notably in the basalt flows of Michigan's Keweenaw Peninsula, and can develop a dark brown or green patina through oxidation.
Is this copper nugget?
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 copper nugget with a known reference. Copper Nugget 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. Streak: copper-red.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: reddish-brown, copper-red, tarnished brown, green.
- 5Look at form & habitCrystal system: cubic. Typical habit: massive, dendritic, arborescent, wire, nuggets.
Often confused with
Copper Nugget vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Copper Nugget leaves copper-red, Cuprite leaves brownish red, shining; luster reads metallic on Copper Nugget and adamantine to submetallic, earthy on Cuprite.
How to tell apart: Nickeline is the harder of the two (Mohs 5-5.5 vs. 2.5-3); streak differs, so Copper Nugget leaves copper-red, Nickeline leaves pale brownish black.
Often found alongside copper nugget
Minerals reported to co-occur with copper nugget. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu
- Mohs hardness
- 2.5-3
- Density
- 8.9 g/cm³
- Colors
- Streak
- Copper-red
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Massive, dendritic, arborescent, wire, nuggets
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Ornamental
- Host rock
- basaltic lavas, hydrothermal veins, sedimentary rocks
Where rockhounds find copper nugget
1 mapped spotsClassic worldwide localities
- Keweenaw Peninsula, Michigan, USA
- Corocoro, Bolivia
- Tsumeb, Namibia
- Dzhezkazgan, Kazakhstan
Field-hunting tip
Where it forms: basaltic lavas, hydrothermal veins, sedimentary rocks. If you start seeing calcite, quartz, prehnite in float, you are in the right ground. Typical habit: massive, dendritic, arborescent, wire, nuggets. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in California. Start trip planning there.
More copper nugget photos
Common questions
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Find copper nugget on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
