A massive chunk of "floating gold" has been found in the belly of a dead whale beached on the Spanish island of La Palma. The highly valuable substance — called ambergris — is a waxy material secreted by sperm whales when they swallow indigestible material such as squid beaks.

Ambergris is used to make perfumes and can sell for thousands of dollars per pound. The chunk found in the Canary Islands weighed about 21 pounds (9.5 kilograms) and could sell for approximately $550,000, according to The Guardian, which first reported the story.

Antonio Fernández Rodríguez, an animal health researcher at the University of Las Palmas, was digging inside the washed-up whale's carcass to try and figure out how it died when he came upon a chunk of something stuck in the whale's intestine, The Guardian reported.

The ambergris seemed to have ruptured the whale's intestine, leading to its death and eventual beaching.

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Only 1% to 5% of sperm whales (Physeter macrocephalus) are found with ambergris — a secretion from the bile duct that is believed to coat indigestible objects the animal has eaten. Normally whales regurgitate these objects, but when they don't, the ambergris helps protect the whale's organs from the sharp material.

This rare substance has been used in perfume-making for hundreds of years because it can help a scent stick to a person's skin — and while synthetic alternatives have since been invented, some companies still use it for certain fragrances.

Sperm whales were one of the most sought-after species in the historical whaling industry, and over-hunting caused their population to plummet. But while the global sperm whale population appears to have stabilized since the decline of whaling in the late 20th century, the species is still considered vulnerable.

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Sperm whales are given the highest level of protection under the Convention on International Trade in Endangered Species, an international treaty banning the sale of various threatened species and their parts. But because ambergris is considered an animal waste product, it isn't covered by the treaty and is legal to sell in many countries. (Though not, notably, in the United States, where it is banned from sale and ownership because it is part of a protected animal.)

In the European Union, which includes the Canary Islands, trade of ambergris is legal. Rodríguez told The Guardian he's hoping to sell this newly discovered chunk and use the proceeds to support victims of a 2021 volcanic eruption on La Palmas, which devastated parts of the island, causing an estimated $929 million in damages.