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Gold is a rare metallic element with a melting point of 1064 degrees centigrade and a boiling point of 2808 degrees centigrade. Its chemical symbol, Au, is short for the Latin word for gold, ‘Aurum’, which literally means ‘Glowing Dawn’. It has several properties that have made it very useful to mankind over the years, notably its excellent conductive properties and its inability to react with water or oxygen!
This stems back to ancient times in the Mediterranean /Middle East, when a carat became used as a measure of the purity of gold alloys (see next Question 5). The purity of gold is now measured also in terms of fineness, i.e parts per thousand. Thus 22 carat is 22/24th of 1000 parts = 916 fineness.
The gold-containing ore has to be dug from the surface or blasted from the rock face underground. This is then hauled to the surface and milled to release the gold. The gold is then separated from the rock (gangue) by techniques such as flotation, smelted to a gold-rich Dore and cast into bars. These are then refined to gold bars by the Miller chlorination process to a purity of 99.5%. If higher purity is needed or platinum group metal contaminants are present, this gold is further refined by the Who l will electrolytic process to 99.9% purity. Mine tailings containing low amounts of gold may be treated with cyanide to dissolve the gold and this is then extracted by the carbon in pulp technique before smelting and refining.
All metal atoms are made of the same building blocks of protons, neutrons and electrons, but in different quantities, so in theory it could be possible to change base metals into gold or any other metal of value to mankind. In practice, it is achieved only in nuclear reactions, where heavy radioactive metals decay into other lighter elements, including some isotopes of gold. However, man’s ancient dream of turning base metals into gold is not a practical proposition. So it remains a dream!
Gold is traditionally weighed in Troy Ounces (31.1035 grams). With the density of gold at 19.32 g/cm3, a troy ounce of gold would have a volume of 1.64 cm3. A tonne of gold would therefore have a volume of 51, 760 cm3, which would be equivalent to a cube of side 37.27cm (Approx. 1′ 3″).
The word gold appears to be derived from the Indo-European root ‘yellow’, reflecting one of the most obvious properties of gold. This is reflected in the similarities of the word gold in various languages: Gold (English), Gold(German), Guld (Danish), Gulden (Dutch), Goud (Afrikaans), Gull (Norwegian) and Kulta (Finnish).
Gold is made into a large number of different bars of different weights. The most well known are the large ‘London Good Delivery Bars’ which are traded internationally. These weigh about 400 Troy Ounces, i.e. 12.5 kg/ 27 lbs. Each. Others are denominated in kilogram’s, grams, troy ounces, etc. In grams, bars range from 1 g up to 10 kg. In troy oz, from 1/10 tr.oz. up to 400 tr.oz.. Other bars include tola bars and Tael bars.