Definition of "mica"

mica

/ˈmaɪ.kə/

noun
countable and uncountable, plural micas
1. (mineralogy) Any of a group of hydrous aluminosilicate minerals characterized by highly perfect cleavage, so that they readily separate into very thin leaves, more or less elastic.
  Quotations
  His little eyes glittered like mica discs with curiosity, though he tried to keep up a bit of superciliousness.
  1899 February, Joseph Conrad, “The Heart of Darkness”, in Blackwood’s Edinburgh Magazine, volume CLXV, number M, New York, N.Y.: The Leonard Scott Publishing Company, […], part I, page 214