Chemical Formula: Cu3(PO4)(OH)3 Locality: Star of the Congo mine, near Lubumbashi, and at the Kalabi and Lukini mines, Katanga Province, Congo (Shaba Province, Zaire). Name Origin: Named for Jules Cornet (1865-1929), Belgian geologist.
Cornetite is a rare secondary copper mineral that is noted for its deep blue, green-blue to green color. It is found in highly weathered, oxidation zones of copper sulfide ore bodies. It has a good deep color, nice crystal forms and an attractive sparkle, all the ingredients for a popular collection mineral.
Physical Properties of Cornetite
Color: dark blue, green-blue to green. Luster: vitreous. Transparency: Specimens are translucent. Crystal System: orthorhombic; 2/m2/m2/m Crystal Habits: include crystals that are short, rounded, nearly diamond-shaped prisms that are terminated by a dome with trapezohedral faces, also as tiny crystalline druzes, fibrous masses and crusts. Cleavage: absent. Fracture: uneven. Hardness: 4.5 Specific Gravity : approximately 4.1 (above average for translucent minerals) Streak: blue.