Gem Name Chemical Composition Hardness Colour Location Diamond Carbon………..10 10 Colourless, Yellow, Red, Blue, Brown, Pink, Green, Black India, Brazil, S.Africa, Australia Ruby Alumina……98.5 Oxide of Iron..1. 0 Lime…………0.5 8.5 To 9 All Red shades Burma, Siam, Ceylon Sapphire Alumina……98.5 Oxide of Iron...1.0 Lime…………0.5 9 All Blue shades Burma, Siam, Ceylon, Kashmir, Montana, Australia Emerald Silica….……68.0 Alumina…....18.3 Glucina.……12.2 Magnesia….. 0.8 Soda………. 0.7 7.5 to 8 Emerald Green India S. America Siberia Aquamarine Silica….……68.0 Alumina…....18.3 Glucina.……12.2 Magnesia….. 0.8 Soda………. 0.7 7.5 to 8 Colourless, Blue, Green, Yellow India ...