braunite
noun
braun·ite
ˈbrau̇ˌnīt
plural -s
: a brittle brownish black or steel-gray mineral that consists of manganese silicate and occurs massive and as tetragonal crystals (hardness 6–6.5, specific gravity 4.75–4.82)
Word History
Etymology
Councilor Braun, 19th century German treasury official + English -ite