Sapphire is a variety of the mineral Corundum it is the same material as Ruby, consisting of aluminum oxide with trace amounts of elements such as iron, titanium, cobalt, lead, chromium, vanadium, magnesium, boron, and silicon it has a hardness of 9 on the Mohs scale. It has a Refractive Index of 1.76 – 1.77. This beautiful piece of Sapphire from The Umba River in Tanzania weighs 3.92cts and measures 8X7X5mm and is eye clean.