means A group of shiny silicate minerals that cleave into thin, flexible, often transparent sheets, long used for insulation, windows, and that glittery sparkle in rocks and cosmetics.

from From Latin 'mica,' meaning 'crumb' or 'grain' — a tiny morsel, the sort of thing that flakes and glitters. The mineral's name was likely nudged along by association with Latin 'micare,' 'to shine' or 'to flash,' so the word carries both senses at once: a small crumb that catches the light. Whether the shimmer or the crumb came first, the two meanings have been entangled since antiquity.