corundum, sapphire, inclusions.5, synthetic corundum.7, gems

This is the second chart in G&G’s series focused on micro-features often observed in natural, treated, and synthetic gems. Sapphire (figure 1) was chosen because of its enduring importance within the gem trade. Demand for this gem species has been the driving force behind the development of treat ment techniques to improve natural stones and the continued production of inexpensive synthetics. Natural sapphires, which originate in certain ig-neous or metamorphic geologic environments are commonly treated to improve their color or clarity. The most common processes involve heat treatment to improve color. Synthetic sapphires have been pro-duced for more than a century, mostly by melt, flux, or hydrothermal solution methods (Hughes, 2017). All of these materials are widely encountered in the jewelry trade.