Gemstones - treasures of Mother Nature

Gemstones, or gems as referred to in day-to-day usage, are in fact minerals. But rocks as well as organic material like amber, which are cut and polished to be used in decorations, are also called gems. However, gems are considered precious since they are rare and astonishingly beautiful.

Our small country too is blessed with a considerable concentration of invaluable gems scattered in areas such as Ratnapura, Balangoda, Elahera and Okkampitiya. There is even historical evidence to prove that Sri Lanka has been a centre for gems.

It is noteworthy to mention that Sri Lanka falls within the top five nations producing gems at present. A variety of gems such as blue and yellow sapphires, star sapphires, star rubies, moonstones and topaz are found in Sri Lanka.

How are gems formed?

We told you that gems are minerals. Therefore, these are found in rocks, or in gem gravels (stones mixed with sand) which have resulted from these rocks because rocks themselves are made up of one or more minerals.

You all know that the surface of the Earth evolves continuously and therefore gems can be found close to the Earth's surface as well as deep inside. Gems can be found in rivers and other waterways when the gravel containing the gems gets washed off due to erosion.

There are three types of rocks where gemstones are found;

1. Igneous rocks

These are rocks which have solidified from molten (liquified by heat) rocks. Initially, these lie in a molten state, deep beneath the Earth's surface and become solid in situations like volcanic eruptions and some even solidify beneath the Earth.

How fast the solidification happens determines the size of gemstones; slower solidification creates larger gemstones.

2. Sedimentary rocks

These rocks are formed by the accumulation of rock fragments. As time passes, these fragments settle down and harden into rock once again. Sedimentary rocks are normally found in layers and sometimes the gems found here show these layers in them.

3. Metamorphic rocks

Metamorphic rocks are either one of the above two types, which have changed beneath the Earth due to heat and pressure and has resulted in a new form of minerals in it. During this process, gemstones also grow within them.

Treatments applied to gems

Gemstones are often treated to improve the colour or clarity of the stone. Depending on the type and extent of treatment, the resulting gemstones may have a stable colour or a colour which turns back in to its original colour. However, this determines the value of the stone. Following are some of the treatments used with gems:

Heat

Heat can improve the colour and clarity of gemstones. Aquamarines are often heat-treated to remove their yellow tones, change the green colour into the more desirable blue or enhance its existing blue colour to a purer blue. A variety of heat treatments are used on sapphires and rubies to improve both colour and clarity.

Radiation

Most blue topaz, both the lighter and the darker blue shades, are exposed to radiation to change the colour from white to blue. The same is done for green quartz to achieve the yellow-green colour.

Waxing or oiling

Emeralds containing natural cracks are sometimes filled with wax or oil to disguise them. This wax or oil is also colorued to make the emerald appear of better colour as well as clarity. Turquoise is also commonly treated in a similar manner.

Fracture filling

This is all about filling up the fractures of the stone. This method has been in use with different gemstones such as emeralds and sapphires and also with diamonds. From 2006, 'Glass Filled Rubies' have become popular. Rubies are generally filled with lead glass, which considerably improves the appearance of larger rubies in particular.

Gems associated with months

January 	- 	Garnet 
February 	-	Amethyst 
March		-	Aquamarine 
April		-	Diamond 
May 		-	Emerald 
June 		- 	Pearl or moonstone 
July 		-	Ruby 
August	 	-	Peridot 
September 	- 	Sapphire 
October 	- 	Opal or tourmaline 
November	- 	Topaz 
December	- 	Zircon or turquoise 

Artificial gem production

With developments in technology, some gemstones are being manufactured to look like other more expensive gemstones as this is easier than trying to find the genuine stones. For example, cubic zirconia is an artificial diamond composed of zirconium oxide.

The speciality of these artificial stones is that although they look like a particular gem, they do not possess their chemical or physical characteristics.

However, this is not always the case. For example, diamonds, rubies, sapphires and emeralds have been manufactured in labs to possess very nearly identical chemical and physical characteristics of the original variety.

Synthetic corundums, including ruby and sapphire, are very common and cost only a fraction of the price of the natural stones. Larger synthetic diamonds of gemstone quality, especially of the coloured variety, have been manufactured quite recently.

Aravinda Dassanayake