Silver purity is expressed as fineness — the proportion of pure silver by mass, measured in parts per thousand.
The two standards you’ll encounter most often:
- .999 fine (“three nines”) — 99.9% pure silver. This is the standard for American Silver Eagles, most silver bars, and the majority of silver bullion products worldwide.
- .9999 fine (“four nines”) — 99.99% pure silver. The standard for Canadian Silver Maple Leafs and a handful of other premium products.
The practical difference in metal content between .999 and .9999 is one part per thousand — about 0.031 grams per troy ounce. For bullion purposes this is economically negligible. The .9999 standard exists primarily for reasons of precision manufacturing and carries a slight prestige premium in some markets.
Sterling silver (used in jewelry and silverware) is .925 fine — 92.5% silver, 7.5% copper for hardness. Sterling is not bullion. It trades at a discount to pure silver because of the alloy content and the cost of assaying and refining it back to .999+.
Older silver coins (pre-1965 U.S. dimes, quarters, half-dollars) are typically .900 fine — 90% silver, 10% copper. These are often called “junk silver” and trade close to their melt value.
When buying bullion, stick to .999 or higher for clean resale.