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A silicate of aluminium, occurring usually in thick rhombic prisms, nearly square, of a grayish or pale reddish tint. It was first discovered in Andalusia, Spain.

A feldspar closely related to orthoclase, but triclinic. It is chiefly a silicate of sodium, potassium, and aluminium. Sp. gr., 2.57 -- 2.60.

square prisms or octahedrons with pearly luster on the cleavage surface. It is a hydrous silicate of calcium and potassium.

urt with a porch or gallery around three or more sides; especially at the entrance of a basilica or other church. The name was extended in the Middle Ages to the open churchyard or cemetery.

A borosilicate of alumina, iron, and lime, commonly found in glassy, brown crystals with acute edges.

triclinic crystals approaching pyroxene in angle, and of a greenish black color. It is a silicate of iron, manganese, and lime.

Said of crystalline rocks which contain a relatively low percentage of silica, as basalt. Basic salt (Chem.), a salt formed from a base or hydroxide by the partial replacement of its hydrogen by a negative or acid element or radical.

Basilica.

sms, commonly of a green or bluish green color, but also yellow, pink, and white. It is a silicate of aluminium and glucinum (beryllium). The aquamarine is a transparent, sea-green variety used as a gem. The emerald is another variety highly prized in jewelry, and distinguished by its deep color, which is probably due…

glass of fine quality, made in Bohemia. It is of variable composition, containing usually silica, lime, and potash, rarely soda, but no lead. It is often remarkable for beauty of color.

rious substances. It was formerly used in medicine. It is composed essentially of hydrous silicates of alumina, or more rarely of magnesia. See Clay, and Terra alba.

granular mineral of a grayish or yellowish color, found in Bolton, Massachusetts. It is a silicate of magnesium, belonging to the chrysolite family.

olitic mineral occurring in white monoclinic crystals with pearly luster. It is a hydrous silicate of aluminia, baryta, and strontia.

A variety of enstatite, often having a bronzelike luster. It is a silicate of magnesia and iron, of the pyroxene family.

A mineral, the hydrous silicate of zinc.

al occurring in hexagonal crystals, also massive, generally of a yellow color, containing silica, alumina, lime, soda, and carbon dioxide.

ed, is brittle, and sometimes very hard. Besides carbon, it contains sulphur, phosphorus, silica, etc.

A mineral of a brownish of cherry-red color, commonly massive. It is a hydrous silicate of cerium and allied metals.

A hydrous silicate of magnesium, allied to serpentine, occurring in waxlike masses of a yellow or greenish color.

dral crystals, varying, in color from white to yellow or red. It is essentially a hydrous silicate of alumina and lime. Called also chabasie.