サファイア (スリランカ)

A gemmy Geuda sapphire with a light violet hue, great luster and sharp crystal faces apart from the base fully intact crystal with small twin attached. Geuda sapphire describes a milky, silk hosting sapphire which is suitable for heat treatment, because the silk (titanium oxide) can turn blue during the heat treatment and most case giving a fine strong saturated blue coloration. The Geuda sapphire normally get heat treated by temperatures around 1600 – 1800 °C with reducing atmosphere. The rutile needles will dissolve and Ti³⁺ will be distributed more equally throughout the stone, fast cooling will prevent recrystallization of the rutile the available Ti³⁺ will cause a the blue coloration.