The most common cultured sea pearls are from three different oysters.  Akoya pearls produced principally in Japan and China come from the Pinctada Fucata oyster.  They are generally white or cream colored with pink, green or blue overtones.  Akoyas are generally smaller than either Tahitian or South Sea pearls, typically ranging between 5-9mm sometimes reaching as large as 13mm.  This is the most widely available type of pearl. 

Tahitian "Black" Pearls are produced in the tropical lagoons of French Polynesia and come from the Pinctada Margaritifera oyster.  They come in shades of grey, black, silver, green and mixed colors of predominently green with purple called "peacock".  Sizes generally range between 9mm and 18mm.

South Sea pearls come from Australia, Indonesia, The Philippines and surrounding waters.  They are produced by the Pintada Maxima oyster and are known for their deep lusterous quality and large size.  South Sea pearls are mainly gold or white with pink, green or blue overtones.  These pearls typically range in size between 9mm and 20mm.