Sapphire

Sapphire is a variety of Corundum, which is composed of aluminum oxide. The typical blue color of sapphire is caused by the presence of trace amounts of iron and titanium. Sapphire is one of the hardest naturally occurring substances, commonly used in jewelry and industrial applications.

Chemistry: silicon dioxide ♦ Color: blue, yellow, pink, purple, green, colorless ♦ Cleavage: none ♦ Transparency: transparent ♦ Luster: vitreous ♦ Crystal System: hexagonal ♦ Moh's Hardness: 9 ♦ Localities: Australia, Thailand, Sri Lanka, USA.