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

plural of crystal lattice

(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

plural of crystal ball

Synonym of crystal set

(colloquial) The drug methamphetamine hydrochloride.

(electronics) An early radio receiver, having no electrical power supply except the radio waves themselves; it used a crystal of lead or cadmium sulphide and a wire (the cat's whisker) touching the crystal's surface.

(chemistry) The water present in the crystals of the salts of certain metals; it is weakly bound by electrostatic forces and may normally be removed by heating.

(chemistry, physics) A phase of matter similar to a liquid, in which the molecules are arranged regularly in one or two dimensions. / Material in that phase.

(physics, chemistry) the separation of two solutes from the same solution by using either a solvent or a crystallization temperature such that only one solute is supersaturated and crystallizes out