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Clay that is colored red or brown by the oxides of iron or manganese, and used as a pigment. It is used either in the raw state or burnt. Burnt sienna, sienna made of a much redder color by the action of fire. -- Raw sienna, sienna in its natural state, of a transparent yellowish brown color.

iron containing a large amount of carbon (from three and a half to six per cent) and some manganese. When the manganese reaches twenty-five per cent and upwards it has a granular structure, and constitutes the alloy ferro manganese, largely used in the manufacture of Bessemer steel. Called also specular pig iron, spieg…

A silicate of manganese of an ash-gray color.

A mineral of a grayish-green or bluish color, consisting of the phosphates of iron, manganese, and lithia.

own color, generally with a fibrous, massive structure. It is a fluophosphate of iron and manganese.

A manganese phosphate near triplite, but containing hydroxyl instead of fluorine.

ble degree of heat. Magnets made of it are said to be highly permanent. It often contains manganese.

r colors, obtained from certain natural clays variously colored by the oxides of iron and manganese. It is commonly heated or burned before being used, and is then called burnt umber; when not heated, it is called raw umber. See Burnt umber, below.

An earthy oxide of manganese, or mixture of different oxides and water, with some oxide of iron, and often silica, alumina, lime, or baryta; black ocher. There are several varieties.

A process for the recovery or regeneration of manganese dioxide in the manufacture of chlorine, by means of milk of lime and the oxygen of the air; -- so called after the inventor.

g massive and of a greenish yellow color, also in reddish crystals (troostite) containing manganese.

Tungstate of iron and manganese, generally of a brownish or grayish black color, submetallic luster, and high specific gravity. It occurs in cleavable masses, and also crystallized. Called also wolfram.

ame is often loosely applied to mixtures of zaffer proper with silica, or oxides of iron, manganese, etc. [Written also zaffre, and formerly zaffree, zaffar, zaffir.]