There are many ways of shaping, or ‘cutting’, a gemstone. A person who cuts gems is called a ‘lapidary’. The gems are cut to display their colour, fire, sheen or other beautiful optical effect. Gems are sliced with diamond saws and ground into flat facets or curved surfaces. They are then polished with diamond or ruby powder.
Many clear gems are cut with flat, mirror-like facets. Their angles are carefully set to allow for the way that the light ‘bends’ as it enters and leaves the gem. Each kind of gem has its own special set of facet angles: brilliant cut ruby has different angles from topaz, for example. A faceted gem will twinkle or show its colour well only if it has been cut with correct facet angles.
Different types of cut: (a) emerald, (b) pear, (c) round, (d) oval, (e) marquise.
‘Cabochons’ are gems that have been cut in the shape of a dome. This type of cut shows off bright colours in opaque gems — gems that do not let light through. Cabochons are also made to reveal beautiful tricks of light, such as ‘stars’ in certain rubies and sapphires, the sheen in moonstones, colours in opals and the bright line which can be seen inside the rare, honey-coloured ‘cat’s eye’ gems.
The ‘emerald cut’ is oblong with the corners cut off. Long facets reflect lots of light back from deeply coloured, transparent gems. Some gems are carved so that little scenes, symbols or figure-heads stand out. These are called ‘cameos’. Opals are often cut into cabochons to show off their colours.
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