All precious metals offered under the Hard Assets Alliance are eligible for IRAs. Your IRA can invest in one, one-half, one-quarter, or one-tenth ounce U.S. gold coins, or one-ounce silver coins minted by the Treasury Department. It can also invest in certain platinum coins and certain gold, silver, palladium, and platinum bullion. Certain coins minted by other nations as legal tender may also be IRS-approved.