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nerals, usually of a green color and micaceous to granular in structure. They are hydrous silicates of alumina, iron, and magnesia. Chlorite slate, a schistose or slaty rock consisting of alumina, iron, and magnesia.

sive mineral, greenish in color, and opal-like in appearance. It is essentially a hydrous silicate of iron.

A fluosilicate of magnesia and iron, yellow to red in color, often occurring in granular form in a crystalline limestone.

A hydrous silicate of copper, occurring massive, of a blue or greenish blue color.

A mineral, composed of silica, magnesia, and iron, of a yellow to green color. It is common in certain volcanic rocks; -- called also olivine and peridot. Sometimes used as a gem. The name was also early used for yellow varieties of tourmaline and topaz.

A soft earth, which is plastuc, or may be molded with the hands, consisting of hydrous silicate of alumunium. It is the result of the wearing down and decomposition, in part, of rocks containing aluminous minerals, as granite. Lime, magnesia, oxide of iron, and other ingredients, are often present as impurities.…

h which the chief eruption comes; similarly, the mouth of a gevser, about which a cone of silica is often built up.

n silky fibers of a lavender blue color. It is related to hornblende and is essentially a silicate of iron and soda; -- called also blue asbestus. A silicified form, in which the fibers penetrating quartz are changed to oxide of iron, is the yellow brown tiger-eye of the jewelers.

A mineral consisting principally of silicate of iron, and crystallizing in hexagonal prisms with perfect basal cleavage; -- so named from the Swedish mineralogist Cronstedt.

occuring in thin-bladed crystals and crystalline aggregates, of a sky-blue color. It is a silicate of aluminium. [Written also kyanite.]

A mineral occuring in octahedral crystals, also massive, of a reddish color. It is a silicate of iron, zinc manganese, and glicinum, containing sulphur.

A borosilicate of lime, first found at Danbury, Conn. It is near the topaz in form. Dana.

A borosilicate of lime commonly occuring in glassy,, greenish crystals. [Written also datholite.]

A hydrous silicate of copper, occurring in emerald-green crystals.

A sort of stone, found in the mines with the true alum rock, chiefly of silica and iron.

A grayish white zeolitic mineral, in tetragonal crystals. It is a hydrous silicate of alumina and baryta.

c in crystallization; often fibrous and massive; color grayish white or greenish. It is a silicate of magnesia with some iron. Bronzite is a ferriferous variety.

tachio) color, occurring granular, massive, columnar, and in monoclinic crystals. It is a silicate of alumina, lime, and oxide of iron, or manganese.

A crystallized, transparent mineral of the Zeolite family. It is a hydrous silicate of alumina and lime.

light green, transparent crystals, affording a brilliant clinodiagonal cleavage. It is a silicate of alumina and glucina.