White tabular colorless crystals of the rare Sn-mineral brannockite from the TL: Foote Mine, Cleveland County, North Carolina, United States of America. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Brannockite
Brannockite is an IMA-recognized mineral species in the silicate class, with the chemical formula KSn₂(Li₃Si₁₂)O₃₀.
It crystallizes in the hexagonal crystal system (space group P6/mcc). It is a member of the Milarite structural group.
Key properties: specific gravity 2.98; Vitreous luster; optically uniaxial.
IMA symbol Bra, IMA status: approved, named in 1972.
Found in the late hydrothermal portions of a Li-Sn-rich pegmatite, in vugs and on flat fracture surfaces.
It is found associated with Bavenite, pyrite, tetrawickmanite, stannian titanite, albite, quartz.
The mineral was named to honor Dr. Kent Combs Brannock (1923–1973), Kingsport, Tennessee, USA, chemist and mineral collector.