During the 2026 Winter Olympics, interest in curling from fans in the United States has developed from curiosity to full interest among the mixed doubles team of Cory Thiesse and Korey Dropkin who won a silver medal on Tuesday and the women’s team won over Canada during Friday’s round robin session in Cortina.
Much of the fascination for curling probably comes from how different it is from other winter sports like skiing, skating, snowboarding and hockey. Why does the playing surface – called a sheet – look like a giant shuffleboard court? Why are the players sweeping the snow? And what are those big stones that slide down the rink towards the goal – or “home?”
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The stones! Those big, heavy discs — weighing between 38 and 44 pounds — aren’t something fans usually find in a sporting goods store or in the basketball aisle at Walmart. At least not a professional, competition-grade curling stone. The stones used for the Olympics are made in a small town factory by a company called Kays Scotland, which makes curling stones by hand for professional and Olympic competition.
Olympic and professional grade curling stones are made in only one place: Ailsa Craig, an island off the coast of Scotland where Common Green and Blue Hone granites are found. (AP Photo/Alastair Grant)
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But the source of the granite used to make those stones is in only one place, an uninhabited island located 10 miles off the coast of the country called Ailsa Craig. Formed by a volcano 60 million years ago, the island – also known as “Paddy’s Milestone” – is made of dense granite, the stuff from which curling stone is created.
A remote island where rolling stones become sounds like a folk tale or the stuff of mythology. But it is true. Ailsa Craig is made of “microgranite” — formed from rapidly cooling magma, via The Athletic — which makes the curling stone ideal for sliding on the ice and staying intact when it collides with other stones during a match.
Jim English, managing director of Kays Curling, examines a granite boulder on the island of Ailsa Craig, off the coast of Scotland, in November 2025. (AP Photo/Alastair Grant)
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The Blue Hone granite, the Common Green granite and the Red Hone granite from the island are distinct from other granites seen and used around the world. The rock has tight molecular structures that make it resistant to water and cracks, according to NASA. That tight grain also helps the granite stand up to polishing and to “clump” as it glides across the ice.
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Kays Scotland has exclusive rights to the Blue Hone quarry, which is highly resistant to water, and Common Green, resistant to collision with other rocks in freezing temperatures, until 2050. The company, based in Mauchline, has been making granite curlers for 175 years.
As might be expected, the growing popularity of curling since it became an official Olympic sport in 1998 has created the need to extract more granite from Ailsa Craig.
Kays Scotland originally took 210 tonnes of rock, enough for at least 1,000 rolling stones. By 2013, the company was harvesting 2,500 tons of Common Green and 500 tons of Blue Hone, The Athletic reported. And according to Kays operations manager Ricky English, this amounts to taking a “scoop” from a tub of ice cream over the life of his deal in terms of available supply.