mining for gold

      Precious Metals


A precious metal is rare and of high economic value. Precious metals are also less chemically reactive than most elements. They have high lustre, and higher melting points than most other metals. The best known precious metals are gold, silver and platinum, although plutonium and uranium could also be considered as precious metals. The latter two will not be discussed in this section.

gold nuggetGold   (Au)
                Gold does not oxidize under ordinary conditions. In its pure form gold has a metallic lustre and is sun yellow. It commonly occurs in its 'native form', that is, not combined with other elements. Its chemical symbol comes from the Latin word for gold "aurum". Because of chemical properties and the fact that it does not tarnish gold was often referred to as "noble" metal.

                Gold was among the first metals to be mined. Ancient civilizations obtained their supplies of gold mainly from deposits in the Middle East. Mines in the region of the Upper Nile near the Red Sea and in the Nubian Desert area supplied much of the gold used by the Egyptian pharaohs. Because of its beauty and malleability, ancient civilizations used gold lavishly in decorating tombs and temples, and gold objects made more than 5,000 years ago have been found in Egypt. Gold was extensively used for the decoration of the Temple of Artemis at Ephesus and in building of the Statue of Zeus at Olympia. These two ancient buildings are among the seven wonders of the ancient world.

platinum nuggetPlatinum   (Pt)
                Platinum is a rare and costly metal. It is one of the densest and heaviest metals, highly malleable, soft and ductile. It is extremely resistant to oxidation and to corrosion by high temperatures or chemical elements as well as being a very good conductor of electricity and a powerful catalyzing agent. Platinum is soluble only in aqua regia (Aqua regia is a 3:1 mixture of hydrochloric acid and nitric acid. Aqua regia is used to test gold and platinum; as it is one of the few substances that can dissolve gold and platinum). Platinum has a silvery-white color and does not tarnish. The name platinum comes from the Spanish word, platina, meaning 'little silver'.

                The "modern" discovery of platinum is attributed to Spanish conquistadors in the 17th century. They discovered it while mining for gold in the Choco region in Colombia. Interestingly, they considered platinum as a nuisance which interfered with the mining of gold. Following the Spanish discovery, platinum was introduced to Europe. But it was scarcely used until the end of the 19th century, because it is a very difficult material to work with. The production of platinum requires very complex processing techniques that were not available until the end of the 19th century. The first person to obtain a pure sample of platinum was W.H. Wollaston, a British chemist whose technique gave foundation to the modern platinum metallurgy. At present South Africa is the major producer of platinum.

                Although platinum is regarded as a "new" metal in its present form, it has a long history. Ancient Egyptians and Pre-Columbian Indian civilizations already valued it as a very important element.

silver nuggetSilver   (Ag)
                Pure silver has a brilliant white metallic luster. Silver is slightly harder than gold but like gold it is very malleable. Pure silver has the highest electrical and thermal conductivity and the lowest contact resistance of all metals. Its chemical symbol comes from its Latin name "argentum".

                Silver was discovered soon after the discovery of gold and copper. Indeed, silver ornaments and decorations have been found in royal tombs dating to about 6000 years ago. Humans learned to separate silver from lead at about 2000BC. Since then silver was regularly used in jewelry and made into coins.

                The earliest known large-scale mines were those in Cappadocia in eastern Anatolia. The best-known of the ancient mines were the Laurium silver-lead deposit in Greece which were actively mined from 500 BC to AD 100. Roman envy of the silver mines worked by the Carthaginians in Spain helped to cause the Punic Wars. By the 16th century, Spanish conquistadors had discovered and developed silver mines in Mexico, Bolivia and Peru. Much richer in silver, these New World mines resulted in the rise of South and Central America as the largest silver-producing areas in the world. In 1859, an extremely large silver deposit -- the Comstock Lode -- was discovered near Virginia City in Nevada. It yielded over 225 million dollars in silver during its productive years and resulted in the United States becoming the world's largest silver producer until the 20th century, when it was surpassed by Mexico and Peru. Today's top producers of silver are: Industrias Penole in Mexico, KGHM Polska Miedz in Poland and BHP minerals in Australia, which produce between them approximately 25% of the world's total mined silver.


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