The largest Scottish freshwater pearl found in living memory is being auctioned, nearly six decades after its discovery.

The Abernethy Pearl is expected to fetch between £40,000 and £60,000 when it goes under the hammer on Wednesday August 21.

The pearl was discovered by William (Bill) Abernethy, who was credited as Scotland’s last dedicated pearl fisherman.

He found it in 1967, before the pearl fishing ban was introduced in Scotland in 1998.

Weighing 43.6 grains, it is the largest freshwater pearl found in Scotland in modern history, although it is smaller than the Kellie Pearl which was discovered in the 1540s and is set in the Scottish Crown.

Mr Abernethy, who died in 2021 aged 96, never disclosed exactly where in Scotland he made the rare find.

It is thought only one in every 5,000 mussels found in Scottish rivers contains a pearl, and generally they are smaller than their saltwater counterparts.

During the 1970s, award-winning wildlife cameraman Doug Allan worked with Mr Abernethy as a pearl diver.

In an obituary, Mr Allan noted his friend was able to discern from the size and shape of the mussel if it contained a pearl.

This enabled him to pick carefully and leave other mussels undisturbed.

He said: “Mr Abernethy was a unique man and it was a privilege to have known him.

“I recall watching Mr Abernethy fishing with his glass and stick and then he gave me a go. It didn’t take long to appreciate just how much hard graft it was.

“Mr Abernethy, of course, made it look effortless. Which it wasn’t. He’d be there, bent over the glass, peering down at the river bed, picking out the small lips of the shells that were buried in the sand.

“I loved learning something of the old craft from Mr Abernethy. The old words that only the real pearl fishers would use. We’d walk sometimes for miles over the fields until we reached ‘the spot’. He’d point out the specific part of the river that he knew would be best for pearls.”

It is believed the Abernethy Pearl, affectionately known as Little Willie, could have been growing in its mussel for more than 80 years before Mr Abernethy found it, meaning it was created during the reign of Queen Victoria.

Trained to fish for pearls by his father Robert, Mr Abernethy had a rare understanding of the mussels and the rivers in which they could be found.

It is believed he wrapped the pearl in a dock leaf to keep it from scratching before he took it to Cairncross of Perth jewellers, where it remained.

At the time, shop owner Alistair Cairncross said: “As the shapes and qualities of the pearls which are found vary very subtly, we design the pieces of jewellery in an asymmetrical form so that their differences are featured rather than hidden.

“Being unusual, we feel that they deserve a treatment which is different, so we have created a series of designs atmospheric of the background in which they were found.”

The pearl will be auctioned at Lyon and Turnbull’s Edinburgh auction house as part of the Cairncross Collection of pieces from the Perth jewellers, with bids also accepted online.

Ruth Davis, Lyon and Turnbull head of jewellery, said: “The Cairncross Collection offers a final opportunity to obtain a piece of Perthshire history.

“As well as antique jewellery, including a beautiful pair of diamond stud earrings weighing over 4.00cts, the collection also includes more contemporary pieces, from high-end designers such as Picchiotti and enamelled jewels by Victor Mayer, as well as a selection of Scottish river pearls.

“The Abernethy Pearl is, of course, the star of the sale and we’re excited to see the interest the auction will undoubtedly generate.”