Winter Olympics
From island to ice
While the Milano Cortina 2026 Winter Games embrace cutting‑edge sporting technology, the equipment for one event remains rooted in tradition. Curling stones are still carved from ancient Scottish rock and shaped much as they were half a century ago.
Every curling stone that slides across the ice at the Winter Olympics in Cortina d’Ampezzo traces its origin back to this windswept island off the west coast of Scotland, a place so protected that access is limited to short windows in winter under ecological supervision.
The island has limited infrastructure and has been uninhabited since 1990. It is leased from the Marquess of Ailsa to the Royal Society for the Protection of Birds until 2050. Kays of Scotland have exclusive harvesting rights for the granite.
Harvesting is allowed intermittently, typically in winter, when seabird nesting is minimal. Blasting is prohibited. Heavy machinery, including loading trucks and excavators, are brought in temporarily and removed once the work is done. Rat traps are laid as a precaution; the island has been rat-free since the 1990s. Its ecological status is closely guarded by conservators.
“It’s a nature reserve, effectively,” said Ricky English, Operations Manager at Kays of Scotland, the sole manufacturer of curling stones made from Ailsa Craig granite.
The graphic illustrates on rocks fall off the island’s huge sea cliffs and are collected at the shore.
Two granites for two jobs
Stones used by elite curlers are made from two distinct types of granite found on the island. One is the blue hone, a fine-grained stone with low permeability which is used for the surface of the curling stone that touches the ice. It is coupled with the common green, a tougher stone that can absorb shock when it collides with another stone.
The combination matters more than rarity. As geological studies have shown, neither granite is entirely unique but their grain size distribution and the presence of unstrained quartz contribute to durability under impact, while blue hone’s exceptionally low permeability may reduce susceptibility to freeze-thaw effects.
This shows the type of granite formations for common green and blue hone and what they look like if it was a sample. It’s an illustration and isn’t too scale.
The blue hone’s relatively uniform grain structure, typically 0.1 to 0.3 millimetres, is less likely to be plucked out during play, keeping the running surface consistent over time. Larger grains are more prone to pitting, which degrades performance, according to Dr. Derek Leung, a mineralogy professor at the University of Regina in Canada whose research examines curling stone damage and mineralogy.
Harvesting a nature reserve
The work is slow by design. Years pass between harvests. When harvesting is permitted, blocks weighing several tonnes are collected from the island and shipped to the mainland. Each boulder of granite weighs between 6 to 10 tonnes.
Nearly all curling stones used at previous Winter Olympics originate from this island. The only exception were curling stones at the 2002 Salt Lake Winter Olympics that came primarily from Welsh granite from the Trefor quarry.
This is a map that situates the reader on where exactly the Ailsa Craig Island is in proximity to the United Kingdom and Ireland
From boulder to “cheese”
On the mainland, granite blocks are sliced into slabs using diamond-wire saws. Cylindrical blanks are drilled out. These blanks are known in the workshop vernacular as “cheeses,” as they resemble a wheel of cheese. “From 1 tonne of granite we get around 20 cheeses,” said English.
The granite is allowed to dry to expose hidden fractures before further work continues. Rejected pieces can be repurposed by the company.
This illustrations show the slabs are made into cheeses before they’re ready to be shipped off the workshop.
Methods to shaping
The Kay’s workshop has modernised gradually. Until around the mid-20th century, curling stones were shaped largely by hand, using chisels in a process closer to sculpturing than manufacturing.
In the 1960s, they began working with the local engineering firm Andrew Barclay & Sons to introduce machinery that helped them move away from fully hand-carved stones. Lathe stations followed in the 1970s but much of the equipment in use today is decades old. They avoid CNC machines and rely instead on trained hands to achieve consistency.
The graphic shows stones use to be made and now how mechanical lathes have been introduced to help shape the stone.
This is all a look and feel job, says English in explaining how craftsman gauge the stone’s shape. Even with the use of mechanical lathes, stone masons still have to regulate their speed as they’re being shaped.
Each common green stone is shaped individually with a slightly hollowed base and a running band of blue hone just 5 to 6 millimetres wide. Only that narrow ring ever touches the surface of the ice.
Assembling and Polishing
A single stone can take up to five hours of hands-on work. Stones are made by joining two blue hone granite components with industrial adhesive to either side of the common green cheese.
Once this is completed, it starts to resemble a curling stone. The glued pieces are then ready to be polished into the finished product.
The blue hone inserts sandwich the common green stone in this illustration
The running surface is polished progressively by a stone mason working by feel. The striking band, the surface of stone that collides with other stones during play, is shot-blasted, not smoothed, to reduce chipping during impact.
a depiction of a stone mason polishing and shaping the curling stone till its perfect
Testing till perfect
More stones are made than needed for the Olympics. For 2026, 164 stones were made but only 132 will be used. Each one is weighed, balanced and visually inspected. They are also acoustically tested as craftsmen listen for changes in tone that signal internal flaws.
Unlike most sports where equipment has exact specifications, stones can vary in weight. Officially they must weigh between 17.24 and 19.96 kilograms with the handle, according to the World Curling Federation.
The mechanics of throwing a stone
Curlers apply a gentle rotation on the handle when they release the stone. Only the blue hone band at the bottom of the stone is in contact with the ice. The rotating stone interacts with the pebbled ice surface, generating friction on one side of the running band.
This resistance makes the stone start to curl in the same direction as the rotation. It’s a gradual change in direction so even the slightest rotation at the release can produce a significant curve.
This illustration shows how the stone behaves on the ice when it is thrown by a curler.
Sweeping or rubbing the ice in front of the stone flattens the surface allowing the stone to travel further at a relatively higher speed. When trying to control speed, two sweepers rub the ice in front of the path of the stone.
Sweeping also affects how much a stone will curl. When sweepers create friction on one side of the stone’s path by warming and flattening the ice surface, it reduces friction and allows the stone to start curling.
Sweeping before the stone helps reduce friction and often the trajectory of the stone. This illustration explains that.
How players read a stone
“When delivering the stones, you get a sense of weight and curl, and you always compare to teammates’ stones and also the opposition.” said Eve Muirhead, who won gold for Britain at the 2022 Olympics.
Teams time each throw with a stopwatch and watch how much the stone curls. They compare the behaviour of the stones within their team and with their opponents’ throws.
This is what a curling stone looks like with a bolt that goes through it as well as showing it’s dimensions.
“If you know your stone maybe curls slightly more or is slightly faster/slower, you have to change your throw or shot selection to accommodate this,” added Muirhead.
Confidence in a stone’s behaviour directly affects shot selection under pressure, she said.
Built slowly, used for decades
Around 15 people make all the elite curling stones for the Olympics at Kays of Scotland’s workshop. A full Olympic set takes weeks. Once ready for play, stones can last 20 to 40 years with occasional refurbishment. Some are reconditioned while others become trophies or souvenirs of past championships.
At the Milano Cortina 2026 Winter Games, one of the most technologically advanced sporting events in the world still depends on this stone. It doesn’t look like much at first, but the curling stones from Ailsa Craig granite are a product of traditional techniques which are the centerpiece to this sport often dubbed ‘chess on ice’.
Sources
Royal Society for the Protection of Birds; SSSI and Special Protection Area (SPA) designations under Habitats Regulations; Leung, D. et al. (2022) — Taking Rocks for Granite: An Integrated Geological, Mineralogical and Textural Study of Curling Stones Used in International Competition; American Geophysical Union, Study on permeability of Ailsa Craig Blue Hone granite (2012); Kays of Scotland; Scottish Geology Trust; World Curling Federation
Edited by
Simon Scarr and Peter Rutherford
Additional development work by
Sudev Kiyada and Han Huang