Most gems are single crystals of a mineral, with a specific chemical composition and atomic structure so perfectly ordered that the gemstone is transparent. Of the 120 minerals known to have been used as gemstones, only about 25 are in common use in jewellery today. Diamond, emerald, ruby and sapphire are some of the precious ones. Others like the topaz, amethyst, opal and aquamarine are said to be semi-precious.
Most gems are unusual forms of common minerals. For example, diamond is a different form of carbon like the less valuable, graphite, which is the substance in the lead pencils. Diamonds are crystals of pure carbon, which are hard and brilliant in its sparkle. On the other hand, graphite is dull and grey.
Natural or rough diamonds look like small pebbles of cloudy glass. When they are cut and polished they sparkle. The most valued diamonds are either colorless or blue-white. Diamond is the hardest known natural substance and can be cut only with another diamond. They were formed under great heat and pressure mostly in cores of volcanoes. They are found in igneous rocks. The largest producers of diamonds are South Africa, Siberia, Australia, Brazil and India.
Quartz is a very common mineral common mineral found in sand and many other rocks. A perfect quartz crystal sometimes contains traces of iron and manganese in it. If it is purple color it is called amethyst. They are chiefly found in the Ural Mountains, India, U.S.A., Uruguay and Brazil. If the quartz is yellow then it is a citrine.
The mineral beryl forms crystals chiefly in granite. The emerald and the aquamarine are two forms of beryl. The emerald is a clear green in color and naturally occurs in Colombia, the Ural Mountains, in Russia, Zimbabwe and Australia. Aquamarine is light blue in color.
Not all gems are minerals. There are some gems like pearls and amber which are really not gems in the true sense. They are actually organic gems as they have organic origins. They are formed with the help of animals and plants. For example, pearls are gems, which are formed inside the shells of oysters. Both the oyster and nature combine together to form the pearl. Similarly, amber is the fossilized remains of the resin of pine and fir trees, which have been buried under rocks for million of years.
Man today has perfected the art of manufacturing synthetic gems. Similar conditions as there were in the earth’s crust during which these gems were formed, are created in the laboratory. Minute diamonds can be made synthetically from graphite. They are used as cutting tools like the dentists drill, glass-cutters and saws for cutting rocks. Synthetic rubies are used in lasers. Synthetic sapphires and emeralds have also been made successfully. General Electric Co. in U.S.A. first produced synthetic gems in 1955.
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