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A form of silica, or silicon dioxide (SiO2), occurring in hexagonal crystals, which are commonly colorless and transparent, but sometimes also yellow, brown, purple, green, and of other colors; also in cryptocrystalline massive forms varying in color and degree of transparency, being sometimes opaque.…

Consisting chiefly of quartz; containing quartz.

Massive quartz occurring as a rock; a metamorphosed sandstone; -- called also quartz rock.

A form of crystal common with quartz, consisting of two six- sided pyramids, base to base.

Containing, or resembling, quartz; partaking of the nature or qualities of quartz.

Quarzose.

Quartzose.

Quartz occurring as gangue in a vein.

A semipellucid, uncrystallized variety of quartz, presenting various tints in the same specimen. Its colors are delicately arranged in stripes or bands, or blended in clouds.

A variety of crystallized quartz, of a purple or bluish violet color, of different shades. It is much used as a jeweler's stone. Oriental amethyst, the violet-blue variety of transparent crystallized corundum or sapphire.

es, occupied, wholly or in part, by nodules or geodes of different minerals, esp. agates, quartz, calcite, and the zeolites. When the imbedded minerals are detached or removed by decomposition, it is porous, like lava.

A variety of translucent quartz, spangled throughout with scales of yellow mica. ~= feldspar, a variety of oligoclase with internal firelike reflections due to the presence of minute crystals, probably of hematite; sunstone.

ramids placed base to base; having a pyramid at each of the extremities of a prism, as in quartz crystals.

inally manufactured at Bristol. -- Bristol stone, rock crystal, or brilliant crystals of quartz, found in the mountain limestone near Bristol, and used in making ornaments, vases, etc. When polished, it is called Bristol diamond.

An opaque or milk-white chalcedony, a variety of quartz; also, a similar variety of opal.

A yellow or smoky brown variety of rock crystal, or crystallized quartz, found esp, in the mountain of Cairngorm, in Scotland.

A composite stone (quartz, schorl, and hornlende) in the walls of tin and copper lodes.

A variety of quartz or chalcedony, exhibiting opalescent reflections from within, like the eye of a cat. The mane is given to other gems affording like effects, esp. the chrysoberyl.

A cryptocrystalline, translucent variety of quartz, having usually a whitish color, and a luster nearly like wax. [Written also calcedony.]

An impure, massive, flintlike quartz or hornstone, of a dull color.