Mercenaria mercenariaNorthern Quahog clam speciesCoastal waters of the North AtlanticDescribed by Linnaeus in 1758, the Quahog pearl does not come from an oyster but rather a thick-shelled edible member of the clam family. Depending on their size they are sometimes marketed as "littlenecks" if they are smaller, "cherrystone" if they are medium-sized or "quahogs" if they are larger. They are also known as "chowder" clams. One of the longest-lived North American bivalves, its life expectancy is sometimes greater than 40 years. It is estimated that only 1 in 100,000 Quahog clams actually produce a pearl of any kind and most are too unattractive for use in jewelry. Before its use in jewelry, the Quahog was used as the nation's first domestic currency. The Wampanoag tribe used a medium of exchange called wampum which consisted of beads made of the shell of the Quahog bivalves.The rarest Quahogs are those which are a true purple—and these are found only in New England. Actually a "calcareous concretion", Quahogs are similar to pearls in that they are started by a parasite. However, the purple stain of the Quahog colors the pearl, not the nacre, in much the same way that a conch pearl is created. Most are below 10 carats with a flat-based button shape, usually with a dark or light purple color, and tales of their accidental discovery while eating clams are not uncommon. The present pendant centers on a large, purple saltwater non-nacreous pearl, of drop shape, graduating slightly in color from pale lavender at the top to deep aubergine towards the bottom, weighing approximately 22.5 carats and measuring 17.60 x 13.05mm, mounted in a two-color 18K gold laurel leaf and ball motif frame, suspended from a delicate chain, length 16 inches.