Pearl weight is expressed in carats or grains when describing natural pearls, or kilograms, kan or momme when describing cultured pearls.
When Is Pearl Weight Used Instead Of Size?
Most of the time, pearls are described primarily in terms of their size (diameter) and expressed in millimeters, such as this pair of akoya pearl earrings. Weight is typically only described within the wholesale trade or when dealing in rare wild pearls such as abalone or conch.
The Different Ways Pearl Weight Is Expressed
Pearl weights are generally expressed in: carats, grains or momme. Typically, cultured pearl weights are expressed in metric kilos, or the ancient Japanese measurement of weights: kan and momme. Natural pearl weights are expressed in carats and grains.
One carat = 4 grains = 200 milligrams = 1/5 gram
One grain = 1/4 carat = 50 milligrams = 1/20 gram
One momme = 18.75 carat = 3750 milligrams = 3.75 grams
One kan = 18,750 carat = 3750 grams = 3.75 kilos
Wholesale Pearls Are Usually Bought by Pearl Weight
When pearls are purchased wholesale, they are often purchased by weight in lieu of strands. The most common standard of weight used when buying Chinese pearls is the kilo. When shopping for pearls in Japan, the kan and momme is standard. English units of weight, or ounces and pounds, are never used in wholesale trading, although the standard measurement of length for any given strand or hank of strands is in inches.
A short, fun video of a wholesale jewelry show, courtesy of PearlParadise.com.
A Pearl The Size Of A Bowling Ball!
The largest pearl ever recorded was originally called the "Pearl of Allah" but is now known as the "Pearl of Lao Tzu", due in part to a fabled legend fabricated by the first Western owner of the gem, Mr. Wilburn Cobb. This huge pearl was discovered by a pearl diver, near the island of Palawan in the Philippines in 1934. This pearl is 238 millimeters in diameter (over 9 inches!) and weighs in at 6.4 kilograms! That's 6400 grams (over 14 pounds), or 1,280 carats! It is a natural, non-nacreous pearl, produced by the Tridacna gigas, or Giant Clam. To put things into perspective, a 7.5 millimeter cultured pearl will weigh about 3 carats, or 3/5 gram. The current value of the Pearl is unknown, although the last known sales price was a mere $200,000.
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