An unidentified fisherman in the Philippines kept a giant pearl that might just be the biggest ever under his bed for the last 10 years.

The gem measuring around 30cm wide and 67cm long is heavier and larger than the current record holder Pearl of Lao Tzu, also known as the Pearl of Allah, by over five times.

It was revealed to the public on Monday (Aug 22) after the fisherman showed it to a local tourism officer in city of Puerto Princesca on Palawan Island in western Philippines.

He had not been aware of the massive pearl's value and kept it for a decade as a good luck charm, until a fire forced him to move out of his wooden shack.

According to the Daily Mail, tourism officer Aileen Cynthia Amurao said the pearl, found off the coast of Palawan, had been formed inside a giant clam.

She said: "The fisherman threw the anchor down and it got stuck on a rock during a storm. He noticed that it was lodged on a shell and swam down to pull up the anchor, and also brought the shell with him. This was a decade ago and he kept it at home."

The fisherman's find, which weighs 34kg, is estimated to be worth US$100 million (S$135 million). The Pearl of Lao Tzu, also found in the Palawan sea, weighs 6.4kg and is worth US$35 million.

She added: "We were amazed when he brought it to us. We now need help from gemologists to fully certify it.We're waiting for authentication from Gemologist Institute and other international authorities.

"But we believe Puerto Princesca is likely to earn another prestigious title and a record breaker for having the world's biggest natural giant pearl from a giant clam."

She said the pearl would remain in the Philippines and hopefully help attract more tourists to Puerto Princesca.