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Today, more often than not, gold is extracted from ores. These ores often contain relatively little gold. Some of these processes cause environmental concern. The ore is crushed to a powder so as to expose the small gold particles. These are dissolved by treatment of the rock with cyanide solution in air. The result of this is a gold cyanide complex. Addition of zinc powder to the resulting solution precipitates out the gold.
4Au + 8NaCN + O 2 + 2H 2O > 4Na[Au(CN) 2] + 4NaOH
Na[Au(CN) 2] + Zn > 2NaCN + Zn(CN) 2 + Au (s)
USİNG:Until today,gold is taken out in the earth.The centre bank confiscate it. Gold is usually alloyed in jewellery to give it more strength, and the term carat describes the amount of gold present (24 carats is pure gold). It is estimated that all the gold in the world, so far refined, could be placed in a single cube 60 ft. on a side. It is metallic, with a yellow colour when in a mass, but when finely divided it may be black, ruby, or purple.
It is the most malleable and ductile metal; 1 ounce ( 28 g) of gold can be beaten out to 300 square feet. It is a soft metal and is usually alloyed to give it more strength. It is a good conductor of heat and electricity, and is unaffected by air and most reagents.
The most common gold compounds are auric chloride (AuCl 3) and chlorauric acid (HAuCl 4). A mixture of one part nitric acid with three of hydrochloric acid is called aqua regia (because it dissolved gold, the King of Metals). It is unaffected by air and most reagents. It is found free in nature and associated with quartz, pyrite and other minerals. Two thirds of the world's supply comes from South Africa, and 2/ 3 of USA production is from South Dakota and Nevada. Gold is found in sea water, but no effective economic process has been designed (yet) to extract it from this source.At now we want to say about marble a few informations. Marble is one of the most sophisticated of stones. It is generally smooth and polished, although it can come in a rough texture. Its use historically is very widespread in both art and architecture. Marble is a kind of limestone that has undergone a process which has made the structure of the rock more solid. This process allows the stone to take a high polish. This stone is generally formed when limestone is faced with extremes of pressure or temperature that cause it to undergo a process known as metamorphism. When Metamorphism occurs the structure of the limestone becomes crystal in nature, transforming into calcite or dolomite. These two substances are the main materials in marble. The crystal is a very strong molecular form and the result of this is a stronger, highly polish-able stone, with unique coloring characteristics often known as Marbling. Today marble is used in stone home furnishings, floors, counters, clocks, hot plates, tables, pillars, structural resurfacing, even bathroom applications. It can be found in almost every country in the world. Its style and versatility make it one of the ideal choices for building materials and structural supply.
At last years when the world production quantity is investigated,the best increase are granit marble's production.China export half of granit and marble as a raw. Except europian countries China is the first number who has 8.000 furnaces and has a kind of natural Stones.Most of industry is 9 provinces and has 13.000 ateliers.
