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milar compounds; thus, barium peroxide is the highest oxide of barium; while nitrogen and manganese peroxides, so-called, are not the highest oxides of those elements.

A manganesian kind of epidote, from Piedmont. See Epidote.

Manganese dioxide, occurring in tetragonal crystals nearly as hard as quartz.

A hydrous oxide of manganese, occurring in smooth, botryoidal forms, and massive, and having an iron-black or steel-gray color.

Manganese dioxide, a mineral of an iron-black or dark steel- gray color and metallic luster, usually soft. Pyrolusite parts with its oxygen at a red heat, and is extensively used in discharging the brown and green tints of glass (whence its name).

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.

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.

with moderate rapidity, without quenching. Such steels are alloys of iron and carbon with manganese, tungsten and manganese, chromium, molybdenum and manganese, etc. They are chiefly used as high-speed steels. -- Self`-hard"en*ed, a.

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.

A manganesian variety of garnet.

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.