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The Mineral Cuprite (Cu2O) is a major ore of copper and is still mined in many areas of the world. Except for native copper, cuprite gives the greatest yield of copper per molecule since there is only one oxygen atom to every two copper atoms. As a Michigan mineral specimen, cuprite shows fine examples of well-developed cubic crystal forms. Cuprite's dark crystals show internal reflections of the true deep red inside the almost black crystal making it desirable for jewelry.

PHYSICAL CHARACTERISTICS:

Color is red to a deep red that can appear almost black.
Luster is adamantine or submetallic to dull or earthy if massive.
Transparency: Crystals are transparent to translucent.
Crystal System is isometric; once thought to be 4 3 2 but now believed to belong to 4/m bar 3 2/m.
Crystal Habits include the cube, octahedron, dodecahedron, and combinations of these forms. Some display faces of the obscure gyroid form. A variety known as Chalcotrichite forms long needle-like crystals or fuzzy crusts. also massive.
Cleavage is fair in four directions forming octahedrons.
Fracture is conchoidal.
Hardness is 3.5-4
Specific Gravity is approximately 6.0 (very heavy for translucent minerals)
Streak is brick red.
Associated Minerals are limonite, copper, chrysocolla, malachite and other secondary copper minerals.
Other Characteristics: Forms a surface film with long exposure to strong light. Crystals of cuprite are sometimes altered or partially altered to malachite and rarely copper.
Best Field Indicators are color, crystal form and softness.

Links

Cuprite

Cuprite Gemstones

Conglomerate from Allouez Mine, Keweenaw County, MI
Found Oct 7th, 2005 Can you see the 1 cm Cuprite Crystal?

Cubic Cuprite Crystals with Chrysocolla and Copper Oxide

Same Crystals, different angles, some with red reflection

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