Due to over-harvesting, pollution, and environmental change, pearls now occur in the wild very rarely. In fact, natural pearls are among the rarest gems in the world. Thanks to pearl farming, consumers have ready access to cultivated or cultured pearls. These pearls still form inside mollusks as they do in the wild, only the pearl farmers carefully maintain the growing environment. Three strand cultured pearl necklace. Photo courtesy of liveauctioneers.com and Litchfield Auctions.