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The appearance of the surface of a mineral as affected by, or dependent upon, peculiarities of its reflecting qualities.

Any crude mixture of mineral or organic matters in the state of a thin paste. Ure.

fusible with difficulty, but easily oxidized. Its ores occur abundantly in nature as the minerals pyrolusite, manganite, etc. Symbol Mn. Atomic weight 54.8.

A mineral related to the micas, but low in silica and yielding brittle folia with pearly luster.

mass; not necessarily without a crystalline structure, but having no regular form; as, a mineral occurs massive. Massive rock (Geol.), a compact crystalline rock not distinctly schistone, as granite; also, with some authors, an eruptive rock.

A fine white claylike mineral, soft, and light enough when in dry masses to float in water. It is a hydrous silicate of magnesia, and is obtained chiefly in Asia Minor. It is manufacturd into tobacco pipes, cigar holders, etc. Also called sepiolite.

A mineral of a red, or brownish or yellowish red color. It is a chromate of lead; -- called also phoenicocroite.

A mineral occurring in small yellow crystals, found in the lavas (melilite basalt) of Vesuvius, and elsewhere. [Written also mellilite.]

A mineral of a honey color, found in brown coal, and partly the result of vegetable decomposition; honeystone. It is a mellitate of alumina.

Pertaining to, or derived from, the mineral mellite. Mellitic acid (Chem.), a white, crystalline, organic substance, C6(CO2H)6, occurring naturally in combination with aluminium in the mineral mellite, and produced artificially by the oxidation of coal, graphite, etc., and hence called also graphitic acid.…

An iron-black or steel-gray mineral, consisting chiefly of the oxides of iron and titanium. It is commonly massive, but occurs also in rhombohedral crystals. Called also titanic iron ore, and ilmenite.

The process or operation of obtaining the mercury, in its fluid form, from mercuric minerals.

To obtain mercury from, as mercuric minerals, which may be done by any application of intense heat that expels the mercury in fumes, which are afterward condensed. [R.]

A zeolitic mineral, grayish white or yellowish, occuring in delicate groups of crystals, also fibrous massive. It is a hydrous silicate of alumina, lime, and soda.

Pertaining to, produced by, or exhibiting, certain changes which minerals or rocks may have undergone since their original deposition; -- especially applied to the recrystallization which sedimentary rocks have undergone through the influence of heat and pressure, after which they are called metamorphic rocks.…

An alteration in a mineral or rock mass when involving a chemical change of the substance, as of chrysolite to serpentine; -- opposed to ordinary metamorphism, as implying simply a recrystallization. -- Met`a*so*mat"ic, a.

A mineral of an iron-black color, and very sectile, consisting principally of sulphur, antimony, and silver.

The name of a group of minerals characterized by highly perfect cleavage, so that they readily separate into very thin leaves, more or less elastic. They differ widely in composition, and vary in color from pale brown or yellow to green or black. The transparent forms are used in lanterns, the doors of stoves, etc., be…

A mineral of the feldspar group, like orthoclase or common feldspar in composition, but triclinic in form.

A rare mineral of resinous luster and high specific gravity. It is a tantalate of calcium, and occurs in octahedral crystals usually very minute.