Sterling silver is considered as a precious metal with an alloy of 92.5% silver and 7.5% other base metals. Sterling silver will oxidize over time. You can restore its luster with a polishing cloth.
10 Karat and 14 Karat gold
10 karat gold is an alloy of 42% pure gold and other metals which give it its hardness. 14k Karat Gold has a higher gold content of 58% pure gold. Both are considered precious metals. Since gold can tarnish from chlorine, please avoid wearing it in spas and swimming pools.