Diamond is a form of crystalline carbon and is the hardest mineral on Earth. Diamonds crystallise in the mantle and are brought rapidly to the surface by volcanic eruptions. An old volcanic ‘pipe’ at Argyle in Western Australia provides unusual champagne (pink to brownish) gem diamonds. The ‘four Cs’ – carat, colour, clarity and cut – determine the value of a stone.

The Argyle Diamond Mine, in the East Kimberley region of Western Australia, is one of the world's largest diamond producers. The deposit was discovered in 1979 and mining commenced in 1983. About 5% of diamonds produced by Argyle are high-quality gem, 70% are near gem and 25% are industrial grade.