What does fineness measure?
Fineness tells you how much of a product is the metal itself, in parts per thousand. A bar marked .9999 fine gold is 99.99% gold; the remainder is trace alloy. Karat is the older jewelry scale, 24 karat is pure, 22 karat is .9167 fine.
Higher fineness isn't automatically 'better' for every purpose. Some alloys add durability, the American Gold Eagle's 22-karat composition makes it harder-wearing than pure gold, while its gold content is still a full troy ounce.
Why does fineness matter for an IRA?
Because the IRS defines eligibility in fineness terms. Gold must generally be .995 fine, silver .999, platinum and palladium .9995, with the Gold Eagle written in as a statutory exception. A product below the threshold can't enter the account.
This makes fineness the first filter for any IRA purchase, before design, brand, or premium enter the conversation.
How does fineness show up in practice?
It's stamped directly on bars and coins and printed in the product specifications on any proper quote, '1 oz .9999 fine gold.' If a quote describes a product without stating its fineness, ask for the full specification in writing.