INCI name
Mica
Also listed as: CI 77019 (when used as a pigment)
Mica is a naturally occurring silicate mineral that shears into thin, shiny plates. In makeup it gives shimmer in eyeshadow, highlighter and lipstick. Synthetic fluorphlogopite is a laboratory-made alternative that can look similar and is listed under its own INCI name.
Some natural mica has been linked to child labour in mining, particularly in parts of India. That is a supply-chain problem, not a skin-chemistry one. Several large brands now publish mica sourcing policies or use synthetic mica. A label that only says "Mica" does not tell you the source.