The Collaborative International Dictionary
Opal \O"pal\, n. [L. opalus: cf. Gr. ?, Skr. upala a rock, stone, precious stone: cf. F. opale.] (Min.) 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.
Menilite \Men"i*lite\, n. [F. m['e]nilite; -- so called because it is found at M['e]nilmontant, near Paris.] (Min.) See Opal.
n. (context mineralogy English) An opal.
[[File: Menilite.jpg|thumb|right| |alt=|
Menilite is a greyish-brown form of the mineraloid opal. It is also known as liver opal or leberopal (German), due to its color. It is called menilite because it was first described from Ménilmontant ( Paris), France, where it occurs as concretions within bituminous Early Oligocene Menilite Shales.