THE COBALTITE GROUP OF MINERALS

The Cobaltite Group is composed of minerals with a similar isometric or pseudo-isometric structure and related chemistry. The general formula for this group is ABX. The A ion can be either cobalt, nickel, iridium, iron, palladium, platinum, rhodium and/or ruthenium. The B ion is usually a semi-metal such as antimony, arsenic, bismuth and/or tellurium. The X ion is usually sulfur, but can also be antimony, selenium and/or tellurium.

The structure of this group is similar to the structure of pyrite and other members of the Pyrite Group. The general formula for the Pyrite Group is AX₂, with pyrite's formula being FeS₂. The X₂ chemical groups of the Pyrite Group are replaced by B-X chemical groups in the Cobaltite Group minerals. The semi-metals and usually sulfur are bonded together with a covalent bond. If the B-X chemical groups are not ordered, as in the B or the X are randomly placed with respect to each other, then the symmetry of the mineral would belong to the Diploidal Class; bar 3 2/m, a class that, although isometric, lacks any four fold symmetry. But if they are ordered then the symmetry is reduced to the lower symmetry of the Tetartoidal Class; 2 3. This is the lowest symmetry class of the isometric system and contains only three fold and two fold axes. Cobaltite may have even a lower symmetry of orthorhombic; m m 2. Only cobaltite is relatively common with most other members of this group being uncommon to rare.

• Changchengite (Iridium Bismuth Sulfide)
• Cobaltite (Cobalt Arsenic Sulfide)
• Gersdorffite (Nickel Arsenic Sulfide)
• Hollingworthite (Rhodium Platinum Palladium Arsenic Sulfide)
• Irarsite (Iridium Ruthenium Rhodium Platinum Arsenic Sulfide)
• Jolliffeite (Nickel Cobalt Arsenic Selenide)
• Maslovite (Platinum Bismuth Telluride)
• Michenerite (Palladium Platinum Bismuth Telluride)
• Padmaite (Palladium Bismuth Selenide)
• Platarsite (Platinum Rhodium Ruthenium Arsenic Sulfide)
• Testibiopalladite (Palladium Tellurium Antimony Telluride)
• Tolovkite (Iridium Antimony Sulfide)
• Ullmannite (Nickel Antimony Sulfide)
• Willyamite (Cobalt Nickel Antimony Sulfide)