Ailsa Craig’s Microgranite: The Secret Behind Olympic Curling Stones

A 10‑mile uninhabited isle off southwest Scotland, Ailsa Craig, is the world’s only source of the super‑dense granite that powers Olympic curling stones.

The Quest for the Perfect Rock

Jim English, co‑owner of Kays Curling, spent a few seconds on the island’s cliff face, inspecting a boulder for big cracks and large specks. “It’s not just a case of landing a boat and then looking for granite. There’s a particular type of granite we’re looking for,” he said. “We look for ones that have got really tight surface pattern.”

The island’s common green granite forms the body of the stone, while the blue hone granite creates the running surface. The two types are found on opposite sides of what poet John Keats once called the “craggy ocean pyramid.”

Olympic Heritage

Kays has supplied every curling stone for the Milan‑Cortina Winter Games. The company’s Olympic history dates back to 1924 in Chamonix, France, where curling was long thought to be an exhibition event but was later confirmed official. Since curling returned as a medal sport in Nagano 1998, Kays has continued to produce stones for each Games.

Founded in 1851, Kays operates from a shop in Mauchline near Ayr. Jim English mused, “We can argue that it’s probably won every gold, silver and bronze medal since the sport became a medal sport back in 1998.”

Kays, also known as Kays Scotland, holds the only license to harvest granite from Ailsa Craig, which is owned by Lord David Thomas Kennedy, 9th Marquess of Ailsa.

Why Ailsa Craig Rocks

Ailsa Craig stands about 1,110 feet tall and spans 2 miles in circumference. It was formed from volcanic activity millions of years ago. The Scottish Geology Trust notes that the island is composed “almost entirely of microgranite,” whose “essentially unflawed nature” makes it ideal for curling stones.

Cold and collisions are key elements of curling. Granite that cracks easily is useless. Ricky English, operations manager at Kays and Jim’s son, explained, “The granite itself has got elasticity properties in it. In a collision, energy is both absorbed and released, so the stone doesn’t split.”

The blue hone granite is essentially waterproof, making it perfect for the running surface. Ricky added, “You can’t get this granite anywhere else in the world but Ailsa Craig.”

The first complete Ailsa Craig stones were used in the 2006 Turin Olympics. Before that, Kays had used some common green from a quarry in Wales.

Harvesting and Crafting

Kays can go years between harvests. The common green “falls off naturally, so we just pick from the site,” Ricky said. Selections weigh between 6 and 10 tons.

The blue hone requires dislodging from the cliff face. Engineers drill and insert a gas charge to break the rock along its natural cracks. Boulders are under 2 tons, so higher quantities can mean fewer harvests.

Boulders are lifted into containers and ferried back to Girvan Harbour. Galloway Granite slices the boulders and cuts round “cheeses” from them, then sends them back to Kays.

The common green granite forms most of the stone, including the striking band around the middle. A hole is drilled through the center of the stone, which weighs on average 42 pounds. The blue hone insert is glued in place, and the handle is attached. On a double insert, blue hone is attached to both sides, and the handle can screw in to either side.

A double‑insert stone costs 750 pounds or $990; a set of 16 costs 12,000 pounds or $15,860. The single‑insert stone is 704 pounds or $930.

Protecting the Island’s Wildlife

Steps on the island protect a large colony of Gannets and some gray seals. Rat traps are set to ensure that boats from the mainland— the trip takes just over an hour— don’t reintroduce rodents to the island.

Curling’s Growing Global Reach

Scottish Curling traces the sport’s local roots back to 1540 in Paisley Abbey. Centuries later, curling is about to launch its first professional league after the Milan‑Cortina Winter Olympics. The Rock League will feature events in the United States, Canada, and Europe.

Kays produces 1,800 to 2,000 stones per year. Canada is its biggest market, while China, Japan, and South Korea are increasing their orders. Ricky English said, “The market in Asia seems to be growing quite a bit. The 2022 Olympics (in Beijing) has maybe just gave it that wee push over there.”

Kays has also sent stones to less‑obvious curling spots like Qatar and Antarctica, where a travel company was using curling as part of a “luxury experience.”

Maguire reported from London.

Takeaways

• Ailsa Craig’s microgranite is the only material used for Olympic curling stones.
• Kays Curling’s unique harvesting and crafting process ensures flawless, elastic stones.
• The company’s Olympic legacy stretches back to 1924, and its stones are now sought worldwide.

The story of Ailsa Craig’s granite shows how a small Scottish island continues to shape a global sport, one stone at a time.