Pearls

Tahitian Pearls

Tahitian Pearls frequently referred to as black pearls, are highly valued because of their rarity. The culturing process for them dictates a smaller volume output and they can never be mass produced because the oyster can only be nucleated with one pearl at a time, while freshwater mussels are capable of multiple pearl implants. In response to the beaded with mantle insertion, the mantle's epithelial cells form a sac which secretes a crystalline substance called nacre, the same substance which makes up the interior of a mollusk's shell, which builds up in layers around the irritant, forming a pearl. Tahitian pearl oysters survive the subsequent surgery to remove the finished pearl, are often implanted with a new bead as part of the same procedure and then returned to the water for another 2–3 years of growth. Black pearls are very rarely black: they are usually shades of green, purple, blue, grey, silver or peacock (a mix of several shades, like a peacock's feather)

Cultured Pearls

Cultured pearls on the market can be divided into two categories, beaded with mantle and only mantle. These pearls are gonad grown, and usually one pearl is grown at a time. This limits the number of pearls at a harvest period. The pearls are usually harvested after one year for akoya, 2–4 years for Tahitian, and 2–7 years for freshwater pearls. In response to the beaded with mantle insertion, the mantle's epithelial cells form a sac which secretes a crystalline substance called nacre, the same substance which makes up the interior of a mollusk's shell, which builds up in layers around the irritant, forming a pearl.

The nucleus bead in a beaded cultured pearl is generally a polished sphere made from freshwater shell. Along with a small piece of mantle tissue from another mollusk (donor shell) to serve as a catalyst for the pearl sac, it is surgically implanted into the gonad (reproductive organ) of a saltwater mollusk. 

Fresh Water Pearls

In freshwater pearls only the piece of  mantle tissue is used in most cases, and is inserted into the fleshy mantle of the host mussel. Multiple pieces of mantle can be inserted in freshwater pearl oysters producing multiple pearls.