THE MINERAL CUPRITE

Chemical Formula: Cu2O, Copper Oxide
Class: Oxides and Hydroxides
Uses: Ore of copper, rarely as a gemstone.
Specimens

Cuprite has been a major ore of copper and is still mined in many places around the world. Of all the copper ores 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 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. Other varieties, such as chalcotrichite, show tufts of needle-like crystals that have a beautiful red color and a special sparkle that make them popular display cabinet specimens.

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.
Notable Occurrences include Arizona, USA; Africa; Australia; Chile and several localities in Europe.
Best Field Indicators are color, crystal form and softness.