Minerals native copper

Copper ore minerals maybe classified as primary, secondary, oxidized, and native copper. Primaryrninerals were concentrated in ore bodies by hydrothermal processes secondary minerals formed when copper sulfide deposits exposed at the surface were leached by weathering and groundwater, and the copper reprecipitated near the water table (see Metallurgy, extractive). The important copper minerals are Hsted in Table 1. Of the sulfide ores, bornite, chalcopyrite, and tetrahedrite—teimantite are primary minerals and coveUite, chalcocite, and digenite are more commonly secondary minerals. The oxide minerals, such as chrysocoUa, malachite, and azurite, were formed by oxidation of surface sulfides. Native copper is usually found in the oxidized zone. However, the principal native copper deposits in Michigan are considered primary (5). 

Berg-kalk, m. rock time (Geol.) mountain limestone. -kiesel, m. rock flint, chert felsite. -kohle,/. (mineral) coal, -kork, m. mountain cork (a light form of asbestos), -kreide, /. rock lime, -kristall, -krystall, m. rock crystal (transparent quartz), -kupfer, n. native copper, -lasur, /. azurite. -leder, n. mountain leather (a form of asbestos), -maun, m miner. 

This element occurs in nature in the uncombined state as native copper and in the combined state as various oxides, sulfides, and carbonates. The chief mineral is chalcopyrite, CuFeS2, from which the element is extracted by roasting (heating in air) followed by reduction. The roasting reaction can be written... 

A single metal may be extracted from several minerals. Thus there are many minerals of copper, such as chalcocite, bornite, chalcopyrite, cuprite, native copper, and malachite one or more of these may occur in an individual deposit. Also, more than one metal may be obtained from a single mineral stannite, for example, yields both copper and tin. A mineral deposit, therefore, may yield several metals from different minerals. 

Cleaning Native Copper. Herb Sulsky, Lithosphere, May 1993, Fallbrook Gem and Mineral Society, http //fgms.home.att.net/copper.htm... 

Copper is distributed widely in nature as sulfides, oxides, arsenides, arsenosulfides, and carbonates. It occurs in the minerals cuprite, chalcopyrite, azurite, chalcocite, malachite and bornite. Most copper minerals are sulfides or oxides. Native copper contains the metal in uncombined form. The principal copper minerals with their chemical compositions and percentage of copper are listed below ... 

Even before 1778, skilled miners were sent from Redruth, Cornwall, to inspect the Lake Superior copper deposits (164). The Medical Repository for 1802 recorded the failure of an expedition to this region. Travellers, it said, have related that there are vast beds of native copper and copper ores of great value on the south side of Lake Superior, within the territory of the United States. A resolution which passed both Houses of Congress in 1800 authorized the President of the United States to employ an agent to ascertain on what terms the mines might be purchased for the government. Because of procrastination this opportunity was lost (165). 

CUPRITE. The mineral cuprite, cuprous oxide. Cu 0. occurs as isometric crystals, usually octahedrons, hut may he cubes, dodecahedrons or modified combinations, it also is found as a massive, earthy material. Its fracture is conchoidal to uneven brittle hardness,, 1.5-4 specific gravity, 6.14 luster, submetallic to earthy color, red nearly transparent to nearly opaque. Its streak is shining brownish-red. Cuprite is a secondary mineral resulting doubtless from the oxidation of copper sulfides. It is often found associated with native copper, malachite and azurile. 

Occurrence. Small amounts of native copper are found in the Lake Superior region and elsewhere in the United States. The principal source of this metal, however, consists of compound ores found in Montana, Utah, Arizona, and New Mexico. Of a rather wide variety of copper-bearing minerals, the most important are chalcopyrite (CuFeS2), chalcocite (CU2S), malachite [Cu2(0H)2C03], and bornite (Cu5FeS4). Most other countries produce important quantities of copper Chile is one of the chief sources. 

Figure 2 Copper minerals and native copper from right to left bomite (front and back) mixed malachite and azurite (front and back) native copper (front) covellite (front) chalcopyrite (back) and chalcocite...

An extensive suite of supergene minerals, including chlorides, sulfates, and arsenates occurs at the Levant mine, Cornwall, England, where ingress of seawater has influenced the variety of minerals in the suite. In stagnant pools of mine drainage at the mine, cuprite [CU2O] and native copper have precipitated within the ochres (BoweU and Bruce, 1995). 

Our trace element data base now contains analyses of 586 samples of native copper from deposits throughout the world. However, the sample sources are skewed toward the northern United States, especially the Lake Superior region. Trace elements can be considered as those normally found in concentrations below 100 ppm (i.e., below the 0.01% normally used as the lower limit of standard rock and mineral analyses). Trace elements do not play a major part in the physicochemical reactions that take place in the formation of geologic deposits. They are either concentrated in or dispersed throughout rock, mineral, and ore deposits... 

However, it turns out that native copper is extraordinaiily variable in composition even within single sources. Native copper nonnally contains a vaiiable amount of other, nonmetallic minerals including copper sulfides, oxides, and silicates. These other minerals are not ductile but break upon cold-working the copper, which decreases the amounts of these minerals in varying amounts and thus alters the composition. Other elements that are soluble in an alloy solution with copper increase in abundance simply because the ratio of metal to nonmetal changes. 

Experiments on the flotation of other minerals, such as native copper, gold, and Scheelite, an ore of tungsten, have met with success, and will probably be greatly developed during the next few years. The flotation of carbonate and other oxidised ores has been attempted with positive results, but this extension also is as yet in the experimental stage. The general opinion of men of science at the present day... 

Copper(I) oxide occurs naturally as the mineral cuprite. It forms when native copper (copper as an element) is exposed... 

The first metals used were those such as gold and copper, which sometimes were found as native metals (not combined with other elements). These native elements could be shaped into useful materials by hammering or cutting. By 4000 to 3000 b.c.e., minerals of copper, zinc, lead, and tin were heated by burning charcoal in a very hot flame so that these elements could be separated from the ore. Much later, this process was applied to iron ore. The purification of iron had to wait until the development of blast furnaces, in which oxygen was blown through molten iron to purify it. 

Copper occurs in nature as native copper that is, in the free state. Other ores of copper include cuprite, CugO chalcocite, CugS clialcopyrite, CuFeSg malachite, Cu2C03(0H)2 and azurite, Cu3(C03)2(OH)2. Malachite, a beautiful green mineral, is sometimes polished and used in jewelry. 

Copper occasionally occurs native, and is found in many minerals such as cuprite, malachite, azurite, chalcopyrite, and bornite. 

Nonsulfide Ore Flotation. Nonsulfide minerals recovered by flotation include native elements such as graphite, diamonds, copper, gold, and numerous oxides as well as salts such as carbonates, phosphates, tungstates, and the like. Examples of value-bearing nonsulfide, noncoal minerals include... 

Galena, tetrahedrite-tennantite, mawsonite and native silver occur in the copper rich ores but not in ordinary pyritic ores and copper rich ores most commonly occur as offshoots, tongues and veins in the deformed deposits. This suggests that these minor minerals formed during the metamorphic deformation stage accompanied by recrystallization. 

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