How the gram price is derived
Although Australian shops quote per gram, the global market quotes gold in US dollars per troy ounce. One troy ounce equals exactly 31.1034768 grams, so the pure gold (24K) gram price is the ounce price divided by 31.1034768, converted to AUD at the live exchange rate. Lower purities are then a simple multiplication: 22K/916 is the 24K gram price × 0.9167, and 18K is × 0.75.
Australia is one of the world's largest gold producers, and the Perth Mint — owned by the Western Australian government — refines much of it. Dealers quote in Australian dollars per ounce and per gram, converted from the USD spot price at the live AUD/USD rate.