FREQUENTLY ASKED QUESTIONS
Purity refers to the amount (by weight) of pure gold an object has. The most common way of describing purity, particularly in the jewellery industry, is by Carats (Karat in the US). Carats are just the purity expressed in units of 24, such that 100% equals 24 carat and 50% equals 12 carat.
For bullion, refiners and dealers use either percentages or fineness (fine being another word for pure). The table below shows the most common purities.
In wholesale investment precious metal markets, physical gold is traded in bars of approximately 400oz with a purity of 99.50% or more. The reason wholesale gold is traded at 99.50% is because it is much cheaper to refine to this purity than 99.99%, which requires additional processes.
Australian gold bullion coins and bars are made from 99.99% pure gold. In verbal discussions, 99.99% is often referred to as "four nines". You may also hear reference to 999.999% gold - six nines - the purest form of gold ever produced.
In 1957, The Perth Mint produced a gold proof plate of almost six nines as measured by the Worshipful Company of Goldsmiths in London. The Royal Mint was so impressed that it ordered some of the gold as the benchmark for its own standards.
Image: The Perth Mint's Plate 42C - the purest gold ever tested by the Royal Mint with certificate of verification.