COLOUR CHEMISTRY
Rare colours and compositions – alongside their hardness rating on the Mohs scale – can be attributed to a gemstone’s chemical composition
PEARL MOHS HARDNESS: 2.5 TO 4.5
This stone is produced by shelled molluscs in their soft tissue. The type of mollusc and minerals in the environment dictate a pearl’s colour.
CITRINE MOHS HARDNESS: 7
Yellow citrine is coloured by iron or aluminium impurities in its hexagonal structure. Natural citrine is rare.