Cornetite

L’Etoile du Congo Mine (Star of the Congo Mine; Kalukuluku Mine), Lubumbashi (Elizabethville), Katanga Copper Crescent, Katanga (Shaba), Democratic Republic of Congo (Zaïre) © 2006 D. Schläfli
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.

Photos :

Locality: L’Etoile du Congo Mine (Star of the Congo Mine; Kalukuluku Mine), Lubumbashi (Elizabethville), Katanga Copper Crescent, Katanga (Shaba), Democratic Republic of Congo (Zaïre) Picture width 3 mm. Copyright © Stephan Wolfsried
Locality: L’Etoile du Congo Mine (Star of the Congo Mine; Kalukuluku Mine), Lubumbashi (Elizabethville), Katanga Copper Crescent, Katanga (Shaba), Democratic Republic of Congo (Zaïre) Image is 6 mm wide. Copyright © Dominik Schläfli

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Locality: Manto Ruso Mine (Manto Russo), Mantoverde district, El Salado, Chañaral Province, Atacama Region, Chile FOV: 0.95 mm Copyright © Chinellato Matteo
Locality: L’Etoile du Congo Mine (Star of the Congo Mine; Kalukuluku Mine), Lubumbashi (Elizabethville), Katanga Copper Crescent, Katanga (Shaba), Democratic Republic of Congo (Zaïre) FOV: 1.7 cm Copyright © Tony Peterson
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