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y acicular crystals, and in masses which often have a radiated structure. It is a hydrous silicate of alumina and soda.

e, in grayish or greenish masses having a greasy luster, as the variety elæolite. It is a silicate of aluminia, soda, and potash.

A greenish yellow or green mineral, consisting chiefly of the hydrous silicate of iron.

A massive and fibrous mineral of a whitish color, chiefly hydrous silicate of lime.

A mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity.

onastery or adjoining a church, as the space within a cloister, the open court before a basilica, etc.

A whitish mineral occurring in radiated or fibrous crystalline masses. It is a hydrous silicate of lime and soda.

ring crystallized and in cleavable masses, usually white, or nearly so, in color. It is a silicate of aluminia and lithia.

sy colorless mineral occurring in rhombohedral crystals, sometimes used as a gem. It is a silicate of glucina, and receives its name from its deceptive similarity to quartz.

A hydrous silicate of aluminia, lime, and soda, a zeolitic mineral commonly occurring in complex twin crystals, often cruciform in shape; -- called also christianite.

a having generally a peculiar bronze-red or copperlike color and a pearly luster. It is a silicate of aluminia, with magnesia, potash, and some fluorine. It is characteristic of crystalline limestone or dolomite and serpentine. See Mica.

An apple-green mineral having a greasy feel. It is a hydrous silicate of nickel, magnesia, aluminia, and iron.

tocrystalline mineral of a dull grayish or greenish white color. It is a hydrous alkaline silicate, and is derived from the alteration of other minerals, as iolite.

ral, resembling quartz, occurring with castor or castorite on the island of Elba. It is a silicate of alumina and cæsia. Called also pollux.

ision of Radiolaria including numerous minute marine species. The skeleton is composed of silica, and is often very elegant in form and sculpture. Many have been found in the fossil state.

nt, occurring abundantly but always combined, as in the chloride, sulphate, carbonate, or silicate, in the minerals sylvite, kainite, orthoclase, muscovite, etc. Atomic weight 39.0. Symbol K (Kalium).

ng a botryoidal or mammillary structure, and rarely in distinct crystals. It is a hydrous silicate of alumina and lime.

usually of a white or greenish color and pearly luster, consisting chiefly of the hydrous silicate of alumina.

ly of a pale brown or of a gray or grayish green color, consisting chiefly of the hydrous silicate of iron and manganese; -- so called from the odor given off before the blowpipe.

or and composition, as diopside, malacolite, salite, coccolite, augite, etc. They are all silicates of lime and magnesia with sometimes alumina and iron. Pyroxene is an essential constituent of many rocks, especially basic igneous rocks, as basalt, gabbro, etc.