mineral

Native Copper (in coinage alloy)

Copper (Cu)

Hardness: 2.5-3.0 Mohs; Color: Reddish-orange (fresh) to brown or green (oxidized); Luster: Metallic; Crystal Structure: Isometric (Cubic); Cleavage: None; Specific Gravity: 8.94.

Hardness: 2
Color: Reddish-orange (fresh) to brown or green (oxidized)
Luster: Metallic

Identified March 19, 2026More mineral →

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Physical properties

Hardness: 2.5-3.0 Mohs; Color: Reddish-orange (fresh) to brown or green (oxidized); Luster: Metallic; Crystal Structure: Isometric (Cubic); Cleavage: None; Specific Gravity: 8.94.

Formation & geological history

Primary formation occurs in hydrothermal veins and the oxidation zones of copper deposits. The coins in the image appear to be alloyed copper (Bronze/Brass counterparts), which are smelting products from the Holocene epoch (Anthropocene-era artifacts).

Uses & applications

Primary use in electrical wiring, currency production (coinage), plumbing, and industrial alloys like brass and bronze.

Geological facts

Copper was the first metal to be worked by humans around 8,000 BCE. The green patina seen on the top center coin is 'verdigris,' a result of acetic acid or atmospheric moisture reacting with the copper content.

Field identification & locations

Identified in the field by its high density, 'copper-red' streak, and malleability. Commonly found in secondary enrichment zones of copper mines in Arizona (USA), Chile, and the DRC. Collectors look for well-defined 'tree-like' branching (dendritic) crystals.