Gemstones are all broadly fromed in the same way – a liquid containing dissolved chemicals cools and crystals grow!
However, the devil is in the detail…..
….Firstly, extreme pressure is also needed.
Gemstones are rare becuae the correct chemicals need to be present in large enough quantities.
Rubies and sapphires are essentially made from aluminium oxide.
The red colour of ruby comes from traces of chromium. Sapphires colour comes from other elements, for example titanium or iron. Both rubies and sapphires also contain some magnesium and silicon.
Emeralds are made from beryllium aluminium silicate (also known as beryl!)
This posting was adpated from an article the June edition of How It Works Daily (page 41)