Carrollite is a mineral that belongs to the sulfide group. It is a rare copper-cobalt sulfide, with the chemical formula Cu(Co,Ni)_2S_4. It forms in the orthorhombic crystal system, usually occurring as small, dark, metallic-gray crystals. Carrollite can also occur as massive granular or compact veins.
The mineral was first discovered in 1929 in the Kambove District of the Katanga Province in the Democratic Republic of Congo, where it was named after Charles Carroll, an American mining engineer and metallurgist. It is primarily found in hydrothermal ore deposits associated with other copper and cobalt minerals, such as chalcocite, chalcopyrite, and cobaltite.
Carrollite is known for its distinctive metallic luster and high reflectivity. It often exhibits twinning and may have a tetrahedral or octahedral crystal habit. The mineral has a high specific gravity and a Mohs hardness of 4.5 to 5, making it relatively hard and dense.
In terms of its uses, carrollite is mainly of interest to mineral collectors due to its rarity and unique crystal structures. However, its copper and cobalt content can be of economic importance in some areas, as these elements are valuable in various industrial applications, including electronics, batteries, and alloys.
In summary, carrollite is a rare copper-cobalt sulfide mineral that forms metallic-gray crystals or massive veins. It is primarily found in hydrothermal ore deposits and is named after American mining engineer Charles Carroll. While primarily of interest to collectors, its copper and cobalt content can have economic significance in certain industries.
