Rubies and Implants

Fascinating alumina.- The alumina family.- Polymorphs and their amazing effects.- The inside of alumina.- A little excursion into etymology.- How were rubies and sapphires determined in the past?.- How are rubies and sapphires determined today?.- Corundum - the natural aluminum oxide.- How hard is corundum?.- Ruby - the red corundum.- Sapphire - the blue corundum.- Why is ruby red and sapphire blu...