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metal-bearing mineral mass that can be profitably mined. Nearly all rock deposits contain some metallic minerals, but in many cases the concentration of metal is too low to justify miningmining,
extraction of solid mineral resources from the earth. These resources include ores, which contain commercially valuable amounts of metals, such as iron and aluminum; precious stones, such as diamonds; building stones, such as granite; and solid fuels, such as coal and
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 the ore. Ores are usually found concentrated in deposits with a definite gradation of metal concentration from the ore to the surrounding rock. The ore often occurs in veins, which are ore-filled fissures in the rock. The veins vary in thickness from only fractions of an inch to several hundred feet. Minerals with no commercial value, called gangue minerals, are usually found mixed with the ore in the vein. Some veins are buried deep within the ground, but others lie close to the surface. Veins of ore exposed to weathering are often eroded and redeposited in placers and alluvial deposits, e.g., ore-bearing stream and lake gravels or beach sands. Some ores are simple chemical compounds, while others are chemically complex mineralsmineral,
inorganic substance occurring in nature, having a characteristic and homogeneous chemical composition, definite physical properties, and, usually, a definite crystalline form. A few of the minerals (e.g.
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. Important ores of aluminumaluminum
, called in British countries aluminium
, metallic chemical element; symbol Al; at. no. 13; at. wt. 26.98154; m.p. 660.37°C;; b.p. 2,467°C;; sp. gr. 2.6989 at 20°C;; valence +3.
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, ironiron,
metallic chemical element; symbol Fe [Lat. ferrum]; at. no. 26; at. wt. 55.845; m.p. about 1,535°C;; b.p. about 2,750°C;; sp. gr. 7.87 at 20°C;; valence +2, +3, +4, or +6. Iron is biologically significant.
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, manganesemanganese
[Lat.,=magnet], metallic chemical element; symbol Mn; at. no. 25; at. wt. 54.93805; m.p. about 1,244°C;; b.p. about 1,962°C;; sp. gr. 7.2 to 7.45, depending on form; valence principally +2, +4, or +7.

Manganese is a pinkish-gray, chemically active metal.
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, and tintin,
metallic chemical element; symbol Sn [Lat. stannum]; at. no. 50; at. wt. 118.710; m.p. 231.9681°C;; b.p. 2,270°C;; sp. gr. 5.75 (gray), 7.3 (white); valence +2 or +4. Tin exhibits allotropy; above 13.
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 are oxides; important ores of antimonyantimony
[Lat. antimoneum], semimetallic chemical element; symbol Sb [Lat. stibium,=a mark]; at. no. 51; at. wt. 121.760; m.p. 630.74°C;; b.p. 1,750°C;; sp. gr. (metallic form) 6.69 at 20°C;; valence 0, +3, −3, or +5.
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, coppercopper,
metallic chemical element; symbol Cu [Lat. cuprum=copper]; at. no. 29; at. wt. 63.546; m.p. 1,083.4°C;; b.p. 2,567°C;; sp. gr. 8.96 at 20°C;; valence +1 or +2. Copper and some of its alloys have been used by humanity since the Bronze Age.
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, leadlead,
metallic chemical element; symbol Pb [Lat. plumbum]; at. no. 82; at. wt. 207.2; m.p. 327.502°C;; b.p. about 1,740°C;; sp. gr. 11.35 at 20°C;; valence +2 or +4.
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, mercurymercury
or quicksilver
[from the Roman god Mercury], metallic chemical element; symbol Hg [Lat. hydrargyrum=liquid silver]; at. no. 80; at. wt. 200.59; m.p. −38.842°C;; b.p. 356.58°C;; sp. gr. 13.55 at 20°C;; valence +1 or +2.
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, nickelnickel,
metallic chemical element; symbol Ni; at. no. 28; at. wt. 58.6934; m.p. about 1,453°C;; b.p. about 2,732°C;; sp. gr. 8.902 at 25°C;; valence 0, +1, +2, +3, or +4.
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, silversilver,
metallic chemical element; symbol Ag [Lat. argentum]; at. no. 47; at. wt. 107.8682; m.p. 961.93°C;; b.p. 2,212°C;; sp. gr. 10.5 at 20°C;; valence +1 or +2.
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, and zinczinc,
metallic chemical element; symbol Zn; at. no. 30; at. wt. 65.38; m.p. 419.58°C;; b.p. 907°C;; sp. gr. 7.133 at 25°C;; valence +2. Zinc is a lustrous bluish-white metal. It is found in Group 12 of the periodic table.
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 are sulfides. Some metals, called native metals, occur uncombined in nature, e.g., copper, goldgold,
metallic chemical element; symbol Au [Lat. aurum=shining dawn]; at. no. 79; at. wt. 196.96657; m.p. 1,064.43°C;; b.p. 2,808°C;; sp. gr. 19.32 at 20°C;; valence +1 or +3.
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, platinumplatinum
, metallic chemical element; symbol Pt; at. no. 78; at. wt. 195.084; m.p. 1,772°C;; b.p. 3,827±100°C;; sp. gr. 21.45 at 20°C;; valence +2 or +4.
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, and silver. The recovery of metals from their ores is one area of the field of metallurgymetallurgy
, science and technology of metals and their alloys. Modern metallurgical research is concerned with the preparation of radioactive metals, with obtaining metals economically from low-grade ores, with obtaining and refining rare metals hitherto not used, and with the
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a natural mineral formation containing metals in compounds and concentrations that make industrial use of the metals technically and economically feasible. The term “ore” is sometimes also used to refer to certain types of nonmetallic minerals, such as sulfur, barite, graphite, asbestos, and various ores used in agronomy.

A distinction is made between monomineralic ores, which consist of a single ore mineral, and polymineralic ores, which contain several valuable minerals and other, associated minerals with no industrial value. As a rule, ore minerals occur together with associated vein minerals. The ratio between ore and vein minerals varies greatly, depending on the metal and the given deposit. For example, in veins of gold-bearing quartz the amount of gold relative to the mass of the quartz is thousandths of 1 percent. On the other hand, some types of iron ore consist entirely of ore mineral (magnetite, hematite). The content of metals in different ore minerals depends, in turn, on the ores’ chemical composition and varies quite broadly. For example, pyrolusite contains 63.2 percent Mn, whereas rhodonite has 32–41.9 percent Mn.

Based on the chemical composition of the predominant minerals, the following types of ores are distinguished: silicate, siliceous, oxide, sulfide, carbonate, and mixed.

Texture is defined as the spatial arrangement of the mineral aggregates that make up an ore. The texture of an ore may be described as massive, banded, spotted, veined, impregnated, cellular, spheroidal, reniform, or loose. By “ore structure” is meant the shape and size of minerals and rock waste in spatially distinct mineral aggregates and the way the minerals and waste rock are combined in these aggregates. According to structure, ores are classified as equigranular, inequigranular, oolitic (with concentric circular accumulations of minerals), porphyritic (with distinct large grains of minerals in an equigranular mass), and divergent. According to the way ore minerals are distributed, a distinction is made between even, uneven, and extremely uneven distribution. Ores extracted from deposits contained in bedrock are called original ores. Ores that accumulate in loose river, lake, and sea deposits after being washed there by water are called placers or placer deposits.

The physical properties of ores are very important for mining and processing. These properties include hardness, strength, jointing, porosity, specific weight, and melting temperature, as well as magnetic, electromagnetic, conducting, radioactive, and sorptive properties and solubility. The quality of the ore to be processed is determined by the content of valuable and harmful components. According to the content of valuable components, a distinction is made between high-grade and low-grade ore. Minimum reserves, content of valuable components, and the maximum content of harmful impurities permissible in the ore determine the industrial qualities of the ore. The industrial qualities vary according to the conditions in which the ore is found and the techniques used to extract and process the ore. Ores are divided into basic industrial grades according to mineral composition, texture, and ore structure and the equipment used in processing.


Magak’ian, I. G. Rudnye mestorozhdeniia, 2nd ed. Yerevan, 1961.
Smirnov, V. I. Geologiiapoleznykh iskopaemykh, 2nd ed. Moscow, 1969.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


The naturally occurring material from which economically valuable minerals can be extracted.
Specifically, a natural mineral compound of the elements, of which one element at least is a metal.
More loosely, all metalliferous rock, though it contains the metal in a free state.
Occasionally, a compound of nonmetallic substances, as sulfur ore.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


any naturally occurring mineral or aggregate of minerals from which economically important constituents, esp metals, can be extracted
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005