A pile of intestinal slurry isn't something you want to encounter on your morning stroll, but a man in the UK is about to become a whole lot richer because of it. While walking his dog in Anglesey, a small island off the coast of Wales, the lucky beachgoer happened upon a piece of prized ambergris.

Image: Adam Partridge Auctioneers & Valuers

Ambergris is a waxy substance that forms in the digestive systems of sperm whales when a foreign object, often a squid beak, irritates their intestines. The ambergris coats the irritant, much like an oyster coats a grain of sand to form a smooth pearl. Eventually, the waxy ball needs to come out, so the whale will expel it (from one end or the other).

"It's a little bit like a cat coughing up a furball," fragrance historian Roja Dove tells the BBC. And if you're wondering why a fragrance historian is so clued up about whale vomit, you've hit on the crux of this story. Because of its musky odour and ability to fix scents to human skin, ambergris has long been used in the perfumery industry. While illegal in US markets, the gastric goo is still used in Europe and can fetch thousands of dollars per ounce at auction. 

"Nobody in the company had seen ambergris before so we were intrigued and excited when it came in," says Oliver Hancock of Adam Partridge Auctioneers & Valuers, who will be selling the piece in their September lot. Weighing just over one kilogram (2.2 pounds), Hancock estimates it will sell for 5,000-7,000 British pounds (just shy of $11,000). 

Adam Partridge holds the prized piece of ambergris. Image: Adam Partridge Auctioneers & Valuers

Before you hit the beach and embark on your career in whale vomit retrieval, you should know that more often than not, what appears to be ambergris turns out to be something pretty worthless. Back in March, another British beachcomber thought he'd discovered a piece worth $100,000. After some investigation, his "gold" turned out to be merely rock. And just last year, yet another Anglesey find was nothing more than a piece of discarded rubber.

Real ambergris can be identified by its odour, which can also give experts clues to its age and quality. Some describe the smell as reminiscent of farm animals, like that of a well-rotted manure heap, while others find it more marine, like the smell of seaweed on a beach. Over time, that smell becomes more complex and perfume-like. "It isn’t as bad as you would think until you get quite close to it," says Hancock. 

A piece like the one in the photographs can take 20 years to fully refine: evolving from a soft, clumpy, soil-like material to a hard block that fractures like dry clay. "We’re keeping it in our alarmed and secure strongroom until the auction," adds Hancock.