Now, in a fundraising feat, tiny pebbles on the shores of the holy island of Iona, have been sold to fund the training of 12 guide dogs for the blind.
For more than 40 years the Cathro family, who run The Iona Shop in Oban, have been collecting donations for the Guide Dogs for the Blind Association, in return for the unusual keepsakes.
The shop specialises in selling jewellery and gifts made of Iona marble and a small bowl of green marble flecked pebbles sits on the shop counter, beside a guide dogs collection tin.
Alan Cathro, who runs the shop in Queens Park Place, said: "It was all started in the early-1970s by my mum and dad. They took reject guide dogs, the ones that didn't quite make the grade, as family pets.
"It was about the same time we started collecting donations for the stones and for 43 years we have just always done this for the guide dogs."
He added: "I don't know exactly how much we have raised over the years, but it's thousands of pounds.
"The guide dogs association only has records going back to 1984, which shows the shop has paid for seven guide dogs to be bought and trained, but in all it's been 12 since the 1970s.
The shop recommends a £1 or £2 donation per pebble. A Guide Dogs Scotland spokeswoman said: "We're very grateful to staff at The Iona Shop for their dedication to fundraising for us for so many years.
"It currently costs about £50,000 to support a guide dog throughout its working life and we receive no government funding to support this amazing service."
She added: "It's thanks to wonderful people like them that we can provide life-changing guide dogs for people."