Golden sheen sapphire
Golden Sheen Sapphire, is a gemstone variety of the mineral corundum, an aluminium oxide (α-Al2O3). It typically shows a metallic golden colour with common variations being brass, copper and bronze, however metallic blue, green and yellow colouration is also possible. A very rare variation is a metallic red colour.
The name golden sheen sapphire is often shortened to gold sheen sapphire and the name is interchangeable.
Unlike normal sapphire, golden sheen sapphire occurs principally as a result of iron and titanium inclusions, making the gem mostly opaque. In this respect, It is more like opal than other typically clear or transparent gemstone. Identified inclusions are ilmenite, rutile, hematite and magnetite. Particularly prominent is hematite which will often result in the formation of geometric hexagonal patterns within the gemstone crystal.
The term gold sheen was first described by the GIA testing laboratory in Bangkok in 2013. Samples of the gemstone were tested to confirm they were true sapphire and the colour was described as brown, with gold sheen effect.
It is only known to come from one source, an undisclosed mine in the north east of Kenya near the Somali border.
It will exhibit mild to strong color change under warm, cool and direct sunlight.
All cabochon cut will exhibit some degree of asterism.
There are no known heating or treatment methods for golden sheen sapphire. Testing of heat treatment on sample batches has resulted in diminishment of the gold sheen effect, reducing the appeal of the gemstone.
Corundum is a crystalline form of aluminium oxide typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It can have different colors depending on the presence of transition metal impurities in its crystalline structure. Corundum has two primary gem varieties, ruby and sapphire. Rubies are red due to the presence of chromium, and sapphires exhibit a range of colors depending on what transition metal is present.
Golden sheen sapphire, from Kenya