Ruby

Ruby is a red variety of corundum, an aluminium oxide, it’s crystal system is hexagonal (trigonal).

It forms in prismatic, tabular, bipyramidal or rhombohedral crystals. It can also occur in granular or massive habits.

Until 1800, when Ruby was recognised as variety of corundum, red Spinels and Garnets were also believed to be Ruby. The intense red colour of Ruby comes from chromium. In some Rubies, inclusions of titanium oxide cause light diffusion in cabochon-cut stones that can appear as a six-pointed star. Rubies have been mined in Sri Lanka, Burma, Thailand, India, Brazil and the United States.
Ancient legend in Burma held that inserting a Ruby into one’s flesh would make one invulnerable. In European lore during the Middle Ages, Ruby was believed to convey good health, resolve disagreements and remove negative thoughts. It was long revered as a stone of royalty, and the Chinese Emperor Kublai Khan was said to have offered an entire city in exchange for a huge Ruby.