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The world renound ruby mines at Mogok, Burma

The sapphire mines at Bang Kacha, Chanthaburi, Thailand.

Gem mining at Pailin, Cambodia.

Sapphire mining at Bo Ploi, Kanchanaburi, Thailand

Ruby mining at Bo Rai, Trat, Thailand.

The marble village of Sagyin, Shan State, Burma.

Inside Rubies & Sapphires

To many people inclusions in natural gemstones are sometimes thought of as flaws. This rather unfortunate description could imply there is something wrong with the gem but this could not be further from the truth. Anyone who has had the opportunity to explore a ruby or sapphire under a microscope will know that these ‘flaws’ are in fact a work of art produced by nature. Each gem has its own unique inclusions; it is extremely rare to find a gem that is totally free of any inclusions.

Apatite crystal inclusions in Mogok Ruby

 

Un-disolved rutile silk in Ceylon Sapphire

Apart from their natural beauty, inclusions serve many purposes to those who handle gems. Once a ruby or sapphire is un-earthed, it is cleaned and sometimes coated with an oil to examine the inclusions. As high temperature heat-treatment can have a great affect on the gem’s inclusions, it is important for the heat-treater to know if there are any inclusions within the gem, which could cause it to fracture or explode when heated. Any inclusions, which could cause problems during heating, are removed by grinding. There are also inclusions, which cannot be removed because they run too deep into the stone. These can include large crystal inclusions or natural fractures. Other inclusions may not be removed because they are small or unobtrusive.

 

Inclusions can also play a major roll in the improvement of a rubies or sapphires. One classic example of this has to be rutile ‘silk’. Tiny rutile needles sometimes form within the ruby or sapphire host crystal intersecting at 60 and 120 degrees. To the naked eye they can give the stone a sleepy appearance. When the gem is cabochon cut and contains enough silk, with the correct orientation of the crystal, the cut stone will display a 6-rayed star. Rutile silk can also play a part in heat-treatment of rubies and sapphires. As part of its composition, rutile contains titanium oxide (TiO2). If the correct parameters are used in the heating process the titanium oxide along with other impurities will produce a blue colour. An example of this is the Geuda sapphire from Sri Lanka.

Un-disolved rutile silk in Madagascan Pink Sapphire

 

 

Guest crystals in Ceylon Star Sapphire

One of the most important uses of inclusions is for the process of identification. Inclusions can be considered a gem’s fingerprint and can reveal much about the origin of the stone. Inclusions can be used to separate natural and synthetic rubies or sapphires as they often display distinctive inclusions. In recent years the separation of treated and un-treated rubies and sapphires has also become a more significant issue. Inclusions can be used to determine high temperature treatments as inclusions with a lower melting point than the host crystal can partially or completely dissolve, while other inclusions can fracture due to expansion. Inclusions are also useful in determining the geographic origin of a gem. An example of this is the colour swirls or treacle, which is only seen in rubies from Mogok in Upper Burma. In all cases an experienced eye is needed to separate these stones.

 

A 'rain' of tiny guest crystals in a Burmese Blue Sapphire

 

 

 

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