We have seen how crystals are made up of atoms fitted together in regular patterns. These patterns can be made to change — with dramatic results! Black graphite is made of carbon atoms; diamond is also made up of carbon atoms but arranged in a different pattern. By applying huge amounts of pressure the carbon atoms in black graphite can be squeezed together to make a more compact diamond pattern. This process is only used to make industrial quality diamonds. It’s too expensive to make a diamond large enough to be set into a ring.
A hard, sparkling, artificial substance called cubic zirconia (CZ) is made into gems which look just like diamond. CZ gems are much cheaper than diamonds.
Ruby and sapphire furnace
Artificial crystals are made in furnaces. Rows of these furnaces make clear, sausage-shaped crystal rods of ruby or sapphire. These are cut in great numbers to make very inexpensive gems. Other kinds of furnaces are used to make perfect crystals which are used in lasers. CZ crystals are made in special furnaces at temperatures of more than 2,500°C.
Picture Credit : Google