The "Pearl of Allah"

The Pearl of Allah also known as the Pearl of Lao Tzu is the largest pearl in the world. It was discovered in 1934 from the Island of Palawan in the Philippines. It measures 9.45 inches in diameter and weighs 6.4 kg. The pearl was produced by a giant clam, Tridacna gigas, and it is a non-nacreous pearl meaning it doesn’t have the iridescence of true gem pearls, like oyster pearls or mussel pearls. The interior of the pearl does not contain a mother of pearl material, in fact it is porcellaneous.

From Internet Stones, via The Jewelry Blog and Malformalady.