Category:Opal

O"pal, n. Etym: [l. opalus: cf. Gr. upala a rock, stone, precious Stone: cf. F. opale.] (min.)

Defn: a mineral consisting, like quartz, of silica, but inferior to Quartz in hardness and specific gravity.

Note: the precious opal presents a peculiar play of colors of Delicate tints, and is highly esteemed as a gem. One kind, with a Varied play of color in a reddish ground, is called the harlequin Opal. The fire opal has colors like the red and yellow of flame. Common opal has a milky appearance. Menilite is a brown impure Variety, occurring in concretions at menilmontant, near paris. Other Varieties are cacholong, girasol, hyalite, and geyserite.