Welcome to the forum! Sea of Cortez pearls are indeed amazing, not for their size, which tends to be diminutive compared to the larger Tahitians, South Seas, and freshwater baroques and Edisons, but for their dreamy, rare coloration. The Cortez pearl farm (Perlas del Mar de Cortez), located in Guaymas, is the only farm raising these beauties, which come from a different breed of oysters, Pteria Sterna, commonly known as the rainbow-lipped oyster and found in a limited area including the Sea of Cortez. Because of the oysters' relatively small size, the oysters are only cultured once, meaning they are not re-nucleated for a second graft. This could contribute to the luster and vibrancy of the nacre. The farm uses fair trade practices and has very strict quality controls, where any sub-standard pearls never leave the farm and are tossed back into the ocean. The nuclei remain in the oysters a minimum of 18 months to 2 years (I hope others will correct if I am wrong), resulting in a thick deposit of nacre. This ring, featuring a SOC mabe, shows an example of the amazing natural colors one can find in the best quality Sea of Cortez pearls.
Note: The bottom pearl is about 8.5mm; the keshi are much smaller. This is a delicate necklace. 
