Rosette Spherocobaltite Crystals
Spherocobaltite is a cobalt carbonate mineral with the chemical composition CoCO₃, where cobalt is combined with carbonate to form a mineral that is prized for its vibrant color. Known for its rich rose-red to magenta hues, spherocobaltite owes its name to its often spherical or discoidal crystal habit, derived from the Greek word "sphaira" meaning sphere. This mineral crystallizes in the trigonal crystal system, a characteristic shared with other carbonate minerals like calcite, but its tendency to form rounded or disc-shaped crystals sets it apart aesthetically.
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| Spherocobaltite crystals From: Bou Azzer, Tazenakht, Ouarzazate, Souss-Massa-Draâ, Morocco. |
The formation of spherocobaltite occurs under specific geological conditions, primarily in hydrothermal cobalt-bearing deposits. It is not a primary mineral but a secondary one, formed through the oxidation and subsequent alteration of primary cobalt minerals. This process involves cobalt-rich solutions interacting with carbonate-rich environments, leading to the precipitation of spherocobaltite. The mineral is often found in veins or as coatings on other minerals in cobalt-rich ore bodies. It's commonly associated with other cobalt minerals like roselite, erythrite, and annabergite, as well as with cobaltian calcite and dolomite, which can sometimes lead to confusion in identification.
Physically, spherocobaltite has a hardness ranging from 3 to 4 on the Mohs scale, which means it's relatively soft and can be scratched by a copper coin or a knife. It exhibits perfect rhombohedral cleavage, a property typical of carbonate minerals, allowing it to be cleaved into smooth, rhombohedral planes. The luster of spherocobaltite varies from vitreous to pearly, contributing to its allure when polished or when freshly broken.
Formula: CoCO3System: Trigonal
Hardness: 3 - 4
Member of: Calcite Group.