'' GOLD SHEEN'' GEMOLOGY
INTRODUCTION
This new rare gem has its origin in Kenya near the Somalia border. This area belongs to Kenya's North Eastern Province. At the end of 2009 discoverer Tanzim Khan Malik brought a new type of sapphire to the world gem market. it displayed a peculiar weak golden shimmering effect on the basal pinacoid surface. Tanzim Khan Malik, a gem cutter and dealer for over 25 years, identified some exquisite rough as out of the world and started putting all his wealth into financing the mine.
The only known deposit located in Kenya is already depleted of high-quality stones. This provides for the advantage of gold sheen sapphire, which is the transparency in their provenance. These are mineral corundum, having a crystalline phase of aluminum oxide.
TRANSPARENCY
The presence of sheen inclusion near the surface of gemstone creates the goldsheen effect. Of the two factors that impact the colour composition of the stone, only the sheen inclusion influence the transparency. This is directly related to the density of sheen inclusions along the c-axis of a sapphire that leads to an opaque stone, low density produces a fine goldensheen and a translucent stone. The overlap of a layer of yellow sapphire above sheen inclusions significantly enhances the golden colour. In the case of a layer of blue sapphire with sheen inclusions, a blue sheen is created.
CUTTING STYLE
Regardless of the cutting style, the stones are always cut so that the sheen inclusions are oriented parallel to the girdle profile, to emphasise the golden sheen effect. As like all gemstones, they are faceted or cut en cabochon. The average loss of weight is around 60%, depending on the rough and required cut.
The faceted gems were cut into various common and fancy shapes. Many of them were fashioned into checkerboard cuts on the front side and a flat face on the back.
Due to the uniqueness of each gemstone, the matching of pairs- or set- is quite challenging. Pairs possessing the same pattern are possible, requiring a rough piece that is cut in two for each side. This technical produces pairs with perfect matching.
TREATMENTS
The cutting and polishing of rough material is currently the only process imposed on Gold sheen sapphire. The stones sold in the gemstone market are natural with no indication of heat treatment. Previous experiments(unpublished) demonstrated that heat treatments do not enhance the golden sheen effect or the possible 6-rayed star. Thus, there is currently no reason to apply any treatment on "Gold Sheen" sapphires. Samples have been tested in several distinguished laboratories around the world, mentioning the rare and unique golden sheen effect displayed by the stone including; HRD Antwerp, SSEF, GRS, AIGS, GIA, Lotus and many more.
