How Do Pearls Form? Not from a Grain of Sand!The popular myth that oysters form pearls from a single grain of sand is a bit of intriguing folklore, but without merit. In fact, oysters are incredibly adept at secreting sand that regularly gets into its shells in waters laden with sand. On the other hand, the notion that it takes a foreign particulate, irritant, or even organism to trigger an oyster to form a pearl is true.
How Oysters Form PearlsResearch asserts that not a grain of sand, but an invading organism (like a tiny drill worm) as well as a shard of mantle shell or tissue is the genesis of a pearl. The invader or foreign material becomes lodged in the oyster causing it irritation. Unable to dislodge the matter through secretions, the oyster covers it with layer upon layer of aragonite (nacre) forming a pearl. In essence, pearl-development is the oyster's way of neutralizing a threat.
I Found a Pearl in an Oyster!Upon rare occasions people have actually discovered pearls while eating oysters or even while beach combing. Such pearls are definitely rare but also rarely valuable. Most opt to except as a keepsake that people often make into unique pendants to commemorate their unusual find. Quahog pearls, are found relatively often and we see many reports of found quahog pearls over at the pearl-guide.com forums:
I found a purple pearl in a clam I was eating-The Quahog Thread
Quahog pearl found in bowl of steamers
Quahog Lavender Pearl
While the media loves to hype the value of these pearls they really don't carry any monetary value, although the shades of purple are lovely.