Giant clams, also known as Ōgikai (扇貝, fan clam) or Shako, are the world's largest bivalve. They inhabit the shallow coral reefs of tropical to subtropical waters and are the largest species of bivalve. This includes the Tridacna gigas. They are named for their appearance, which resembles a fan. Giant clams are a rare organic gemstone, white like jade, and a Buddhist sacred object. They are one of the four major organic gemstones, along with pearls, coral, and amber. In Chinese Buddhism, they are 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) while using a giant clam rosary will 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. #Rosary #Buddhist prayer beads #Evil warding