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Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Trioctahderal with Mg, some substitutions for of Fe3+ for silicon at the (T) positions and OH>F at (A) otherwise would be Fluorotetraferriphlogopite.
Found in ultrabasic alkaline massif of Kovdor.
Named after its commonly tetrahedral crystals, Tetrahedrite occurs “in hydrothermal veins or contact metamorphism deposits of low to medium temperature of formation.” One of the most common sulfosalts, Tetraherite is found in thousands of localities worldwide.
Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/tetrahedrite.pdf