Historically, many gemstones have been enhanced to
improve their appearance. At the present, a variety of traditional and advanced
enhancements are applied to many natural gemstones such as beryl, corundum,
tourmaline, topaz, zircon, zoisite, etc. Heat treatment (also known as thermal
enhancement) is applied to gemstones such as rubies & sapphires to improve
colour and /or clarity (maybe some phenomena such as asterism). Thermal enhancement
of rubies and sapphires is considered stable and permanent, and
it is generally accepted by the international gem and
jewellery trade.
The
process of thermal enhancement in rubies and sapphires is performed to improve
the colour and /or clarity. This process may incorporate the use of chemicals
such as sodium tetraborate powder, in order to help facilitate.The closure
of fractures by healing or infilling and protect the stones from tension crack
which may happen in high temperature condition.
Before
After
Upon
exposure to elevated temperatures, the chemicals will melt and coat the surface
of the gemstone and enter fractures. When cooling condition start, chemical
melted during the heating process will solidify as an amorphous solid. This
material maybe encountered at the surface of polished gemstone and remain
trapped within areas of the fractures of partially healed by the other way,
the amorphous solids also may result from the thermal alteration and
interaction of naturally occuring inclusions within the host gemstone.
Thermal Enhancement In Rubies & Sapphires
