clear, colourless form of the silica-based mineral quartz, often called "pure quartz" or "clear quartz".

plural of crystal lattice

(mineralogy) A mineral crystal whose interior space is empty

plural of crystal dick

(uncountable, idiomatic, slang) Erectile dysfunction caused by methamphetamine use or other drug use.

(now historical) Crystal; a piece of crystal.

(optics) A uniaxial crystal, such as one of calcite, in which the extraordinary wave travels faster than the ordinary wave / A crystal that contains a cavity

(crystallography) Any of the seven distinct symmetry classifications of crystals: cubic, tetragonal, hexagonal, orthorhombic, monoclinic, triclinic and trigonal.

A small crystal from which a larger crystal of the same substance is grown

plural of crystal sphere