society > occupation and work > materials > raw material > gem or precious stone > rock crystal > [noun] > piece of (4)
crystal (sense A. 2a); (also) a piece of this; †a container made of this (obsolete).
A piece of such a substance, typically considered as a precious stone or as having magical properties.
As a count noun: a piece or specimen of this.
A crystal. Cf. crystal, n. 2c. Obsolete.