clear, colourless form of the silica-based mineral quartz, often called "pure quartz" or "clear quartz"
Colorless transparent quartz, used in optical instruments and as a semiprecious gemstone. Transparent variety of the silica mineral quartz that is valued for its clarity and total lack of colour or flaws. Rock crystal formerly was used extensively as a gemstone, but it has been replaced by glass and plastic; rhinestones originally were quartz pebbles found in the Rhine River. The optical properties of rock crystal led to its use in lenses and prisms; its piezoelectric properties (see piezoelectricity) are used to control the oscillation of electrical circuits
The specimens which enclose hair-like substances are called Thetis's hair-stone, Venus's hair-stone, Venus's pencils, Cupid's net, Cupid's arrows, etc
quartz-like material resembling solid glass not used because of its rarity and high cost
The natural colorless quartz stone used to decorate metal chandeliers before glass was used The term crystal is normally only applied to the natural stone and is not appropriate to use in the description of glass