Lepidomelane
Lepidomelane (lep`i*dom"e*lān) , noun
[Greek lepi`s -i`dos, a scale + me`las, me`laina, black.]
(Mineralogy) An iron-potash mica, of a raven-black color, usually found in granitic rocks in small six-sided tables, or as an aggregation of minute opaque scales. See Mica.