Low-Temperature Heating of Pink Sapphire: Why Detection Can Be Difficult
A pink sapphire with a violet component may become a cleaner pink after heating. Detecting this change can be difficult when the heating leaves little obvious damage inside the stone. The word low-temperature is relative: the temperatures involved are still extremely high. What the experiments showed SSEF’s 2010 article describes research on pink sapphires from Madagascar and East Africa. Heating around 800–1000°C could reduce the blue component. The researchers also studied samples at several lower and higher experimental temperatures. The important lesson is that familiar microscopic signs of intense heating can be scarce after lower-temperature treatment. A stone that lacks melted-looking inclusions is not automatically proven unheated. Zircon inclusions as evidence The study investigated zircon inclusions with Raman spectroscopy. Heating could alter their crystal condition and the shape of their spectral peaks. Measuring these changes provided evidence that was less obvious ...