Team USA received silver in blended doubles curling on Tuesday after reaching the occasion’s remaining for the primary time through the Winter Olympics. In the semifinal towards Italy on Monday, American roller Cory Thiesse made the successful shot that knocked the Italian group’s curling stone out of its place.
The strictly regulated curling stones weigh between 38 and 44 kilos (17 and 20 kilograms) and may final many years. One firm, Kays of Scotland, handcrafts {most professional} and all Olympic stones utilizing granite from a single small uninhabited island off the coast of Scotland.
Granite from Ailsa Craig is exceptionally fine-grained; its minerals are organized in such a method that tightly knits them collectively. This density makes the granite significantly resilient to collisions and permits it to be polished to a end easy sufficient to glide on ice. The distinctive mineral composition additionally provides the stones an intrinsic capacity to curve alongside their trajectory.
“It’s not just about the ability to withstand chips and cracks. It also has to do with how it moves on the ice and how the stones bounce when they hit each other,” mentioned Dr. Bob Gooday, a geological analyst at National Museums Scotland. “Professional curlers have used other kinds of stones, which slide perfectly well, but when they hit each other, they don’t bounce quite the same.”
Mark Callan, the chief ice technician of World Curling and the previous gross sales and technical providers director of Kays of Scotland, mentioned the corporate produces 2,000 to 2,500 stones per yr for 77 international locations.
Curling was one of many first Winter Olympic sports activities, debuting as a medal occasion on the inaugural 1924 Winter Games in Chamonix, France. The sport originated in sixteenth century Scotland, the place individuals slid tough stones on frozen lakes. Curlers take turns sliding granite stones throughout pebbled ice towards their “house,” a round goal marked on the floor.
The curling floor is specifically ready with frozen water droplets that create “pebbles” on the ice sheet, minimizing friction. The pebbled texture reduces floor space contact and prevents the heavy stone from sticking, permitting it to glide extra simply on the ice.
An athlete creates a curved trajectory, often called the “curl,” which will be influenced by as much as two sweepers who use brooms that soften the pebbled ice, lowering friction and permitting the stone to journey farther, typically barely altering its path. Curling is the one sport during which the projectile’s trajectory will be influenced after the athlete releases it.
A curling stone should be heavy sufficient to remain on its meant trajectory, stand up to collision and glide on ice simply sufficient in order that it will probably nonetheless be influenced by sweeping. Most granites are not match for this problem.
“Most granites have very similar chemistry, and they tend to form lots of relatively large quartz and feldspar crystals. That texture obviously isn’t particularly good for curling stones,” Gooday mentioned. Coarse stones with massive crystals chip and fracture simply when knocked collectively.
However, granite from the island Ailsa Crag, which is off the west coast of Scotland, is round 60 million years outdated, Gooday defined. “This is the time that the North Atlantic is opening up, and Europe and North America are separating, so there’s formation of lots and lots of magma,” he mentioned. The Ailsa Craig granite was shaped from the cooling and solidifying of this magma.
Ailsa Craig granite has “slightly strange, unusual chemistry,” Gooday mentioned. Compared with granites worldwide, the rock in Ailsa Craig is extraordinarily low in aluminum. This geological anomaly led to the formation of uncommon minerals excessive in sodium and iron — equivalent to arfvedsonite, aegirine and aenigmatite — that sometimes don’t happen in granite.
For causes scientists nonetheless don’t absolutely perceive, Gooday added, “the unusual mineralogy and the tight, fine structure of the granite itself” make Ailsa Craig granite immune to chipping and preferrred for curling stones.
Three forms of granite are discovered on Ailsa Craig: widespread inexperienced, blue hone and pink hone. Gooday defined that pink hone is blue hone that has been stained by iron supplies. Common inexperienced and blue hone are used to make curling stones, and geochemically, the 2 forms of granite are the identical.
The physique of the curling stone is made with widespread inexperienced. This contains the “striking band,” the place stones collide. Common inexperienced granite accommodates black spots the place uncommon minerals clump collectively, which supplies the stone its “springy nature. These rocks sort of bounce off each other when they hit,” Gooday defined.
Blue hone is used to create the concave backside of the curling stone, which kinds a slim “running band” that permits the stone to glide. This kind of granite has low porosity and permeability, that means that water doesn’t penetrate the stone as simply, preserving it sturdy and constant over time, defined Dr. Derek Leung, an assistant professor of mineralogy on the University of Regina in Saskatchewan and a roller on the Caledonian Curling Club.
This high quality of blue hone is one cause why alternate options to Ailsa Craig granite don’t examine. “We’ve tried to use other materials for the running surface,” Leung mentioned. “One idea is that rocks are natural. They’re imperfect. So, what if we use something synthetic?” He added that members of the curling neighborhood tried utilizing ceramics to construct the working band.
However, Leung defined that ceramics can not retain their texture over time. The roughness of a curling stone is what permits the rocks to curve. As a ceramic stone loses its texture over the course of a sport, it turns into inconsistent and unable to curve.
The curling mechanism of a stone comes from the intrinsic attribute of the granite, “the mineral grains of a certain size that are grown within rock,” based on Leung.
Ailsa Craig granite is so well-suited for curling that the Olympics have by no means used every other form of granite in formal competitors. “There is consensus that Ailsa Craig stones are the best,” mentioned Dr. Matthew McDowell, a lecturer in sports activities coverage, administration and worldwide improvement at Scotland’s University of Edinburgh.
The Grand Caledonian Curling Club, later renamed the Royal Caledonian Curling Club, has required the island’s granite for curling stones since its founding in 1838, he defined. The membership serves as the game’s governing physique in Scotland and standardized the foundations of play.
“Thus, when the Winter Olympics first took place in 1924 in Chamonix, France, the RCCC made the rules for the competition — and that included using Ailsa Craig granite for the stones,” he added.
McDowell mentioned that, traditionally, there has by no means been a push to hunt alternate options to Ailsa Craig granite.
“We know they’ve worked since the 1800s, so why change that?” Leung added.
Sign up for NCS’s Wonder Theory science newsletter. Explore the universe with information on fascinating discoveries, scientific developments and extra.