opal

noun5

1. •
   A mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity, of the chemical formula SiO₂·nH₂O.
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.

   • The witchery of the dawn turned the grey river-reaches to purple, gold, and opal; and it was as though the lumbering dhoni crept across the splendors of a new heaven. — 1889
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.