Another cause of discoloration is due to the corrosion of the metals from which jewelry is made. Pure gold, 24K, itself will not corrode but is too soft for many kinds of jewelry and therefore it is alloyed with proportions of base metals, usually silver or copper to make it harder. The composition of 14 karat gold is 14/24 pure gold and 10/24 alloys. Only the base metal used for alloying corrodes, leaving gold untouched. The chemical compounds of silver and copper that are formed turn very dark even when slightly corroded. This corrosion occurs under moist or wet conditions.
Our skin, in which the jewelry lies, is provided with thousands of perspiration glands. Chemically the perspiration is mostly fat and fatty acids. Theses essentially mild chemicals are enough to cause corrosion of 14 karat gold especially when aided by warmth and free access of air. When this happens remove your jewelry often and use an absorbent powder, free of zinc oxide, on the skin areas that come into contact with your jewelry.
Rings containing copper and silver alloys, particularly sterling silver, corrode readily on the skin if enough salt is present. Simply exposing the hands to salted nuts, crackers, or popcorn can cause such corrosion and discolor the skin. Rings should be taken off when you must expose your hands to salt.
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