Pearl A pearl is a hard object produced within the soft tissue (specifically the mantle) of a living shelled mollusk. Just like the shell of a clam, a pearl is composed of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes (baroque pearls) occur. The finest quality natural pearls have been highly valued as gemstones and objects of beauty for many centuries.
Black coating uses either ruthenium or TIN cobalt black to give a piece of jewelry a light black or completely black appearance. It is very durable and resistant to scratches. Black plating gives the jewelry piece a sense of masculinity and high-tech.