Green Paints are for the most part compounds of copper and of chromium. The best known greens are the following: Bremen green, or verditer, consisting mainly of a basic carbonate of copper. Brunswick green, a hydrated oxychloride of copper; but the name is sometimes given to a hydrated basic carbonate, also known as mountain green. Chrome and emerald green are oxide of chromium. Emerald green is also used as synonymous with Schweinfurt green. English green is a mixture of Scheele's green with gypsum. Guignets green is oxide of chromium prepared in a peculiar way. Hungary green is a kind of malachite found in Hungary. Rinman's green is obtained by heating zincoxide with a cobaltcompound. Saxony green is an indigo colour used in printing. Scheele's green is arsenite of copper, and Schweinfurt green, Veronese green, and Vienna green, are also compounds of arsenic and copper. Verdigris is a hydrated basic carbonate of copper, often seen in copper coins. Besides these are green colours derived from plants. Of these may be mentioned chlorophyll, the green colour of leaves: sap green, the juice of Rhamnus catharticus or buckthorn, made into a green lake with alumina; Chinese indigo-green, etc. Research Green Paint
An earth colour is a pigment derived from the earth, as opposed to chemically manufactured pigments. Earth colours include ochre, sienna, umber, red oxide and malachite with further colours developed by calcining the materials to form for example burnt sienna. Earth colours are very stable and permanent. Research Earth Colour
Azurite is a minor ore of copper with an intense azure-blue colour. It alters to malachite and is associated with limonite, calcite, chalcocite, chrysocolla and other secondary copper minerals.
Azurite reacts vigorously with hydrochloric acid. It has the formulae Cu3(CO3) 2(OH)2 and a relative hardness of 4. Research Azurite
Chrysoberyl is a mineral occurring in granite rocks, pegmatites, and in mica schists. It is frequently found in river sand and gravels in round pieces about the size of a pea, but also crystallized in eight-sided prisms.. It serves as a gem stone: cymophane, orientalchrysolite, alexandrite and 'cats eye' which can be of great value. It has the formulae BeAl2O4 and a relative hardness of 9. *Chrysocolla
Chrysocolla is a hydrous silicate of copper, occurring massive, of a blue or greenish blue colour. It is a minor ore of copper and a mineral of secondary origin, occurring in the oxidised zones of copper veins. It is associated with malachite, azurite, cuprite, native copper. It is named from two Greek words meaning 'gold' and 'glue'. Research Chrysoberyl
Chrysocolla is a hydrous silicate of copper, occurring massive, of a blue or greenish blue colour. It is a minor ore of copper and a mineral of secondary origin, occurring in the oxidised zones of copper veins. It is associated with malachite, azurite, cuprite, native copper. It is named from two Greek words meaning 'gold' and 'glue'. Research Chrysocolla
Conichalcite is a mineral of the adelite group, often brilliant green in colour, it is a secondary mineral that forms in the oxidation zones of copperore bodies. It is often found as an encrustation on rocks composed mainly of limonite, where it is associated with adamite, azurite, bayldonite, linarite, malachite, olivenite and smithsonite. Conichalcite was confirmed as a distinct species of mineral in 1849 and is sometimes used as an ore of copper. Research Conichalcite
Copper is one of the most anciently known metals, deriving its name from Cyprus, large supplies having in Greek and Roman times come from that island. It is a metal of a pale red colour tinged with yellow; chemical symbolCu, atomic weight 63.6. Next to gold, silver, and platinum it is the most ductile and malleable of metals; it is more elastic than any metal except steel, and the most sonorous of all except aluminium. Its conducting power for heat and electricity is inferior only to that of silver. It has a distinct odour and a nauseous metallic taste. It is not affected by water, but tarnishes on exposure to the air, and becomes covered with a green carbonate.
Copper occurs native in branched pieces, dendritic, in thin plates, and rarely in regular crystals, in the primitive and older secondary rocks. Blocks of native copper have sometimes been found weighing many tons. Its ores are numerous and abundant. Of these several contain sulphur and iron or other metal, such as copper glance or vitreous copper (Cua S); gray copper or Fahlerz, one of the most abundant and important ores; and copper pyrites or yellow copper ore (CuFeSg), another abundant ore. The red oxide of copper forms crystals of a fine red colour, and is used for colouring glass.
There are two native carbonates, the blue and the green, the latter being the beautiful mineral malachite, the former also known as blue malachite. Blue vitriol is a sulphate, and is used for dyeing and preparing pigments, as are various other copper compounds. Verdigris is an acetate. The arsenite of copper is the pigment Scheele's green. Schweinfurth green is another copper pigment. All the compounds of copper are poisonous.
Copper is found in most European countries, in Australia and Japan, in Africa and in North and South America (especially in the vicinity of Lake Superior). In Britain the mines of Cornwall have yielded little copper since the end of the 19th century.
Copper is extracted from its ores either by the dry or the wet process. For the former, what is known as the Welsh process is most common in Great Britain. It consists in alternately roasting the ore, and then smelting it in a furnace with a suitable slag, until impure or blister copper is obtained. Before this stage is reached a metallic compound of copper, sulphur, and iron has been produced, technically known as matt, regulus, or coarse metal, and subsequently a tolerably pure sulphide of copper called fine metal. The blister copper is refined by burning off the sulphur, arsenic, and other volatile impurities, and by melting it along with wood charcoal and stirring it with a wooden pole. The quality is then tested, and, if found satisfactory, the copper is cast into ingots.
In extracting the metal from pyrites by the wet process, the ore is first roasted to get rid of the larger proportion of sulphur, then the calcined residue still containing sulphur is mixed with common salt, ground and heated in ovens. The copper is thus converted into chloride, part of which volatilizes, but is condensed, along with arsenic and other substances, by passage through flues and water-condensers. After some hours the calcined mixture is raked out of the ovens, cooled, and transferred to tanks, where it is exhausted by successive treatment with water. The solution, containing chloride of copper, sulphate and chloride of sodium, and iron salts, is next heated along with scrap-iron. Copper precipitates in the form of a ruddy, lustrous, tolerably compact mass, with a crystalline appearance, and mixed with metallic-iron and oxide. The larger pieces of iron are picked out, the precipitate washed and drained, and then rendered compact by heating in a furnace. A slag containing the oxide of iron forms, and the copper, when judged sufficiently pure, is run into moulds.
The crude metal is now usually refined by an electrolytic process, the crude metal serving as anode and a strip of pure copper as cathode. Many alloys of copper, especially those containing tin and zinc, are of much importance, eg, brass, an alloy of copper and zinc; bronze, an alloy of copper with about 8 or 10 per cent of tin; bell-metal, composed of eighty parts of copper and twenty of tin.
Copper is applied to a great many useful purposes. In sheets it is used for the constructing of boilers and stills of a large size, etc; and pipes of various sorts, as well as electircla circuits, wire, lightning-rods, etc., are made of it. It is also used in electrotyping and engraving, for various household utensils and fittings; but its use for household utensils is by no means free from danger on account of the formation of verdigris by the action of acids. Research Copper
Cornetite is a rare, brittle, secondary mineral with a chemical composition similar to turquoise. Cornetite is formed in the weatheredoxidation zones of copper sulphide ore bodies and is found in association with brochantite, chrysocolla, liberthenite, limonite, malachite and pseudomalachite. Cornetite was first discovered in 1912 and was confirmed as a distinct mineral in 1917, subsequently being named after the Belgian geologist Jules Cornet. Cornetite is a naturally occurring hydrous phosphate of copper, as is also turquoise. Research Cornetite
Abbreviations
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