opal

Plural: opals

Noun

• a translucent mineral consisting of hydrated silica of variable color; some varieties are used as gemstones
• A mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity, of the chemical formula SiO₂·nH₂O.
• A mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity, of the chemical formula SiO₂·nH₂O.
• A precious gem, an iridescent gemstone found in the opal-silica mineral substrate (potch)
• The colour of opal: any shade of blue with bright flecks of other colours, such as white, yellow, and red.
• A colloquial name used in molecular biology referring to a particular stop codon sequence, "UGA."
• Any of various lycaenid butterflies of the genus Nesolycaena.