Opal

Noun

1. 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)
2. A precious gem, an iridescent gemstone found in the opal-silica mineral substrate (potch)
3. The colour of opal: any shade of blue with bright flecks of other colours, such as white, yellow, and red.
4. A colloquial name used in molecular biology referring to a particular stop codon sequence, "UGA."
5. Any of various lycaenid butterflies of the genus Nesolycaena.