stilpnomelane

noun

stilp·​no·​mel·​ane

ˌstilpnōˈmeˌlān

plural -s

: a black or greenish black mineral K(Fe,Al)₁₀Si₁₂O₃₀(O,OH)₁₂ (?) occurring in foliated plates, fibrous forms, and velvety bronze-colored incrustations and consisting of a hydrous iron aluminum silicate with a little potassium (specific gravity 2.77–2.96)

Word History

Etymology

German stilpnomelan, from Greek stilpnos glistening + melan-, melas black

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