Gemmology is the science of Gems. The Word ‘Gemmology‘ has been derived from the ‘Gemma‘ meaning ‘Precious‘ and ‘Logy‘ means ‘Study‘. It is the study of Precious material. Today, Gemmology encompasses a large field of studies. From the Prospecting and mining of Gems, treatments and their identification.
Gemstones have been known and worked upon for thousands of years. Experts gem identification was, however, neither needs nor possible upto a very short time ago. The use of glass imitations and the more recent advent of synthetic gemstones have made the scientific study of gemstones essential for any serious Gem-dealer. The ‘eye of experience’ is no longer sufficient for determining the bonafide of stone beyond doubt.
Characteristic of Gemstones or Gem:
The Beauty, is in the eye of the beholder, is as true with gems as it is with many other things. To one beauty may be in the colour; to others, it may be in the Phenomenon resulting from skilful cutting by the lapidary. All the factors contributing to beauty are found in a few precious minerals. The colour diamonds stands pre-eminent Because they not only possess them all but also they have all these in too high degrees.
A gemstone has to durable to have lasting value. It must be able to withstand the wear and tear of daily use. Diamonds, Rubies and Topaz are very hard Gemstones. They are very difficult to scratch or Break and hence ideal for daily use. On the other hand, Pearls, Peridots, etc. are relatively less hard and consequently easily scratched or chipped and therefore, suitable only for occasional use. A gemstone therefore must be durable to be of any great value.
This is the third most important quality gemstones must possess. Any substance having beauty and durability but available in plenty will not attract people greatly. However, a stone that is Available rarely will attract people since its ownership sets them apart from others. Here again, a mineral may be readily available but specimens of good colour and clarity may be very, then such qualities will be sought after in that mineral. Rarity is sometimes influenced by fashion but in the case of more expensive gemstones, this is not the case since they never go out of fashion.
Origin and Occurrences of Gemstone:
out of 2500 mineral, almost 95% of the earth crust is made up of mineral or group of minerals. All of the major earth crust belongs to one of the major types:
These rocks are formed due to the solidification of the molten magma (lava) materials. It is called Primary Rocks.
e.g. Granite, Basalt, Pegmatite, etc.
These rocks are produced by the deposition of material on the earth crust by water, wind, etc. giving rise to alluvial, lacustrine, marine deposits by compacting and hardening of sediments.
e.g. Conglomerates, Limestone, Sandstones, etc.
This rocks are the tertiary rocks formed by the action of heat, pressure and sometimes chemicals on the primary and secondary rocks. Heat and pressure changes the structure and composition of the minerals giving rise to new minerals. Various types of gemstones are found in the metamorphic rocks like Gneiss and Schist. Due to heat and pressure, Limestones changes to marble, sandstone changes to quartzite. In Myanmar, rubies are found in Limestone marble.
e.g. Rubies, Garnets, Spinels, Diamonds are often found in different metamorphic rocks in India.
Other Important Notes:
The mineral is usually a crystalline homogenous substance produced by inorganic process having a definite chemical and physical and optical properties, which is constant within narrow limits.
Quarts, Feldspar, Tourmaline, Mica, Corundum, Beryl are mineral species which have various gemstones variety.
1. Species – Beryl
2. Variety – Emerald, Aquamarine etc.
Rock is a mixture of Minerals. A rock like granite is made up of feldspar, mica, quartz, tourmaline, topaz etc. in varying proportion. Lapis Lazuli is a rock made up of many minerals like sodalite, Pyrite lazurite, hauyne etc.
Pearls, on the other hand, is not a mineral, since A living thing, the Oyster, produces it. It is composed of crystalline calcium carbonate and conchiolin in varying proportion so that it can not have a fixed chemical composition or physical properties.