What is a karat, exactly? It’s the measurement of the purity of gold, on a scale of 24. Something that’s 24-karat gold is 99.9 percent gold. Jewelry is most commonly in the 14k to 22k (58 to 91 percent gold) range because pure gold is too soft to wear; most pure gold is used for investment purposes. Other alloys, chiefly silver and copper, are added to gold to make it sturdy enough for jewelry. The alloys can change the color, too; adding more copper creates rose gold, and adding nickel, manganese, or palladium creates white gold. Just some factors to consider while you’re browsing the vast inventory of men’s gold chains found on eBay.