When gold jewelry causes discoloration of skin, it is due to a chemical reaction between the jewelry and oils on the skin. Most gold jewelry is not actually solid gold and can contain different metals, such as copper or ... More »

The most common reasons for goldfish to turn black are genetics and ingestion of colored food. Dark environments also cause goldfish to produce additional melanin, which results in a change in pigment. Disease is uncommo... More »

Blood turns a deep, dark red that is sometimes blackish in appearance when it becomes deoxygenated. If you are looking at blood not circulating inside the body, it slowly becomes deoxygenated and turns darker and darker ... More »

Gold in its purest form does not leave black or green marks on skin, but the other metals mixed in with gold jewelry, such as copper, nickel and silver, can cause discoloration on skin. Discoloration usually occurs when ... More »

Sterling silver turns black or tarnishes due to a chemical reaction caused by contact with sulfur or hydrogen. Some foods or everyday items containing sulfur can cause tarnishing, but even polluted air can turn sterling ... More »

Clean tarnish from your pure gold jewelry by immersing the jewelry in warm water with a couple of drops of dish soap and rubbing gently with your fingers or a washcloth. Do not use this method for gold jewelry that incor... More »

One can clean gold jewelry at home with everyday materials, including a toothbrush, dish detergent and water. The overall process is simple and only takes 15 minutes. More »