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

A mineral, usually 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.

A common mineral occurring in monoclinic crystals, with a prismatic angle of nearly 90º, and also in massive forms which are often laminated. It varies in color from white to dark green and black, and includes many varieties differing in color and composition, as diopside, malacolite, salite, coccolite, augite, etc. Th…

A bronze-colored mineral, of metallic luster. It is a sulphide of iron, and is remarkable for being attracted by the magnet. Called also magnetic pyrites.

heavy yellow powder consisting of a basic mercuric sulphate; -- formerly called turpetum minerale, or Turbith's mineral.

c element found (combined) in minute quantities in pitchblende, and various other uranium minerals. Symbol, Ra; atomic weight, 226.4. Radium was discovered by M. and Mme. Curie, of Paris, who in 1902 separated compounds of it by a tedious process from pitchblende. Its compounds color flames carmine and give a character…

A fissure or mineral vein traversing the strata vertically, or nearly so; -- called also rake-vein. Gill rakes. (Anat.) See under 1st Gill.

See Rake, a mineral vein.

Arsenic sulphide, a mineral of a brilliant red color; red orpiment. It is also an artificial product.

Having the form or shape of a kidney; as, a reniform mineral; a reniform leaf.

An inflammable mineral resin, usually of a yellowish brown color, found in roundish masses, sometimes with coal.

A variety of the mineral cyanite.

Manganese carbonate, a rose-red mineral sometimes occuring crystallized, but generally massive with rhombohedral cleavage like calcite; -- called also dialogite.

Manganese spar, or silicate of manganese, a mineral occuring crystallised and in rose-red masses. It is often used as an ornamental stone.

A translucent mineral of a green color and micaceous structure, belonging to the chlorite group; a hydrous silicate of alumina, magnesia, and iron; -- called also clinochlore.

powdery variety of calcite occuring as an efflorescence. -- Rock milk. (Min.) See Agaric mineral, under Agaric. -- Rock moss, a kind of lichen; the cudbear. See Cudbear. -- Rock oil. See Petroleum. -- Rock parrakeet (Zoöl.), a small Australian parrakeet (Euphema petrophila), which nests in holes among the rocks of…

A mineral of a hyacinth or honey-yellow color, occuring in square octahedrons. It is an antimonate of calcium.

A green micaceous mineral occurring in minute scales. It is essentially a silicate of aluminia and potash containing vanadium.

hide of arsenic; -- called also ruby sulphur. -- Ruby of zinc (Min.), zinc sulphide; the mineral zinc blende or sphalerite. -- Ruby silver (Min.), red silver. See under Red.

Having the appearance of ruins, or of the ruins of houses; -- said of certain minerals.