Quartz vs. Opal

Difference Between Quartz and Opal
Quartznoun
(mineral) The most abundant mineral on the earth's surface, of chemical composition silicon dioxide, SiO2. It occurs in a variety of forms, both crystalline and amorphous. Found in every environment.
Opalnoun
(mineral) A mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity, of the chemical formula SiO2·nH2O.
Quartznoun
colorless glass made of almost pure silica
Opalnoun
A colloquial name used in molecular biology referring to a particular stop codon sequence, "UGA."
Quartznoun
a hard glossy mineral consisting of silicon dioxide in crystal form; present in most rocks (especially sandstone and granite); yellow sand is quartz with iron oxide impurities
Opalnoun
(entomology) Any of various lycaenid butterflies of the genus Nesolycaena.
Opalnoun
a translucent mineral consisting of hydrated silica of variable color; some varieties are used as gemstones