GEMS – A MIXTURE OF VARIOUS COMPOUNDS

Majority of familiar gems are Oxides or Silicates. A gemstone may be pure chemical element, a simple chemical compound or a more complex mixture of various compounds and elements. Most gemstones are found in igneous rocks and alluvial gravels.
Gemstones have two chief characteristics: hardness and specific gravity. The hardness of a gemstone makes it resistant to scratching. It is described according to a standard scale of 10 minerals known as the Mohs’ scale. The scale is named after F. Mohs, an Australian mineralogist who developed the scale in 1882.
Among the gems, Diamond is the only gem that is composed of a single element, carbon. It is known as the hardest substance found in Nature. Besides hardness Diamond has other unique qualities such as low reactivity to chemicals, clarity. It is also a very good conduct of heat and has the highest melting point.
Opal is a popular gem. It is basically a mineraloid. It reflects different colours and with diffraction of light at various wavelengths. It imparts opal a valuable look.
Cat’s eye is a variety of Chrysoberyl, also called Cymophane. The colour of cat’s eye varies from green or yellow-green to yellow, brown or yellow-brown.
Pearls are organic gemstones formed from Calcium Carbonate. There are natural pearls and cultured pearls. Pearls can almost be any shape, but round ones are generally preferred.
Coral is an organic gemstone. It is the skeleton formed by the individual polyps, the plant – like animals. Corals normally occur in red or pink colours.
Amethyst is the purple variety of quartz. It occurs in a wide range of purple shades. It is available in variously cut forms that suit colour distribution.
Ruby is the red variety of corundum. It is the second hardest natural mineral. The redness of the ruby is caused by the trace elements of chromium. The colour of ruby could be any shade of red up to almost pink.
Emeralds is the green variety of the mineral beryl. A few other gemstones such as aquamarine, morganite and heliodor also belong to this variety. Small amounts of chromium and traces of iron give the wonderful green colour of Emerald.
Garnets are found in highly metamorphosed rocks and some igneous formations. Garnets form under high temperature and pressure. They are transparent, in variable colours and have a high refractive index. They are also hard and durable.
Jadeite is one of the two minerals called jade. It is composed of smallest interlocking crystals that makes it tough material. Jade is known to be stronger than steel. It has the presence of trace amounts of chromium, iron and manganese.
Topaz is a common gemstone. It is known to occur in colours ranging from golden brown to yellow.