美蛋白石

Cacholong \Cach"o*long\, n. [F. cacholong, said to be from Cach,
the name of a river in Bucharia + cholon, a Calmuck word for
stone; or fr. a Calmuck word meaning ``beautiful stone'']
(Min.)
An opaque or milk-white chalcedony, a variety of quartz;
also, a similar variety of opal.

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}.