Precious metal purity guide

Purity, or fineness, tells you what proportion of an item's weight is the precious metal itself. K&J Stack uses this percentage when estimating melt value.

Gold

24K is close to pure gold. Common jewellery standards include 22K (about 91.6%), 18K (75%), 14K (58.5%) and 9K (37.5%).

Silver

Fine silver is commonly marked 999, Britannia silver 958 and sterling silver 925. A 925 item contains 92.5% silver by weight.

Platinum and palladium

Platinum jewellery is often marked 950, meaning 95% platinum. Palladium can also be marked by fineness, including 950 and 500.

Why gross weight is not pure-metal weight

An alloy contains other metals, so a 10 g sterling-silver item does not contain 10 g of pure silver. At 925 fineness, its theoretical silver content is 9.25 g. Stones, non-metal parts and filled or plated construction can make a simple weight × purity calculation inappropriate.

Hallmarks and stamps can help identify fineness, but unusual, antique, plated or uncertain items may need professional testing.