Size of beads: 8mm Giant Clam Also known as Ōgigai (fan shell) and Shako. They inhabit shallow waters of coral reefs in tropical to subtropical seas and are the largest species of bivalve. Includes the Tridacna gigas. It was named for its appearance, which resembles a spread fan. Giant clams are a rare organic gemstone, white as jade, and a Buddhist sacred object. Giant clams, pearls, coral, and amber are known as the four major organic gemstones. In Chinese Buddhism, it is revered as one of the seven treasures along with gold, silver, lapis lazuli, agate, coral, and pearls. Giant clams are one of the seven treasures of Buddhism, and it is said that chanting the nenbutsu (Buddhist invocation) using giant clam prayer beads can bring twice the merit. It is said to calm the mind, be effective against insomnia, and is good to wear for a long time. It is said to heal mental fatigue and be good for visual impairment, and it is also said to have the power to improve fortune, maintain health, and ward off evil.