14k Yellow Gold 12mm Black Onyx Stud Earrings Amazon Curated Collection. $37.05. The natural properties and composition of mined gemstones define the unique beauty of each piece. The image may show slight differences to the actual stone in color and texture.. Wipe gently clean with soft cloth. Do not clean with solvents.. Gemstones may have been treated to improve their appearance or durability and may require special care.