APOPH'YLLITE, noun [Gr. from, and a leaf; so called because of its tendency to exfoliate.]

A mineral occurring in laminated masses or in regular prismatic crystals, having a strong and peculiar pearly luster. Its structure is foliated, and when a fragment is forcibly rubbed against a hard body, it separates into thin lamens, like selenite. It exfoliates also before the flame of a lamp. From its peculiar luster, it is sometimes called by the harsh name, ichthyophthalmite, fish-eye stone.