The Quirky Geology Behind Olympic Curling Stones

The quirky earth science down Olympic curling stones

The rocks utilized successful nan Olympic athletics of curling travel from 1 land successful Scotland and 1 quarry successful Wales. What makes them truthful special?

By Andrea Thompson edited by Seth Fletcher

Eve Muirhead of Team Great Britain competes against Team ROC during nan Women’s Curling Round Robin Session connected Day 13 of nan Beijing 2022 Winter Olympic Games.

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From skating to curling, nan thrilling sports of nan Winter Olympics person plentifulness of subject down them. Follow our sum here to study more.

Athletes often person specialized instrumentality aliases apparel to make them run, swim, skate aliases skis their best, but curling takes things to different level. Curling rocks—as nan round, astir 40-pound stones are called—only travel from 2 places connected nan planet: a small land successful Scotland called Ailsa Craig and nan Trefor granite quarry successful Wales.

But what makes nan rocks from these places uniquely suited for sliding crossed a rectangular slab of crystal toward a bullseye target? And are these really nan only places to find suitable stones?

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To find out, Scientific American said pinch Derek Leung of nan University of Regina successful Saskatchewan, a mineralogist and avid curler who utilized to compete for Team Hong Kong. Leung has joined his 2 interests by doing nan first mineralogical analyses of curling rocks since 1890. “It’s been much than a 100 years since we had looked astatine them,” he says, truthful he wanted to spot what modern subject could show us.

But earlier we get into that, let’s spell complete nan 2 main parts of a curling rock: nan moving aboveground and nan striking surface. The erstwhile is simply a ringing connected nan bottommost of nan stone that skids crossed nan ice, and nan second is simply a set astir nan sides of nan stone that collides pinch different rocks (ideally knocking an opponent’s stone disconnected nan bull’s-eye aliases nudging your team’s person to it).

Derek Leung

Each aboveground needs circumstantial properties to do its job. This is wherever Ailsa Craig and nan Trefor quarry travel in. The erstwhile has been utilized for curling stones since nan early 19th century; nan second since curling grew successful fame aft World War II.

Each spot has 2 types of stone utilized for curling stones: Ailsa Craig communal greenish and Ailsa Craig bluish hone, and bluish Trefor and reddish Trefor. All 4 types are granitoids, which are igneous rocks, meaning they shape arsenic magma aliases lava cools and crystalizes. Ailsa Craig’s rocks formed astir 60 cardinal years agone erstwhile magma pushed into a comparatively shallow furniture of nan Earth’s crust during nan rifting that formed nan Atlantic Ocean. Trefor’s formed astir 400 to 500 cardinal years agone during a mountain-building arena called nan Caledonian Orogeny. Both are, geologically speaking, reasonably young. “Having a young stone is astir apt a bully point because it intends that it's little apt to person incurred stresses related to different tectonic events” earlier it is subjected to nan stresses of curling, Leung says.

Common contented has held that rocks from these 2 sources were perfect because they contained very small quartz, a brittle, silica-based mineral that would beryllium little than perfect for costly stones perpetually knocking into each other. (Curling stones costs astir $600 a pop, and they’re typically utilized for 50 to 70 years.) But Leung recovered that successful truth each 4 rocks incorporate quartz. Yet nether nan microscope, “I recovered almost nary fractures,” he says, apt because of their young age.

Ailsa Craig bluish hone is commonly utilized for nan moving surface; manufacturers trim a circle retired of nan bottommost of nan main stone and insert a disk of bluish hone. Leung recovered that bluish hone has small, reasonably azygous atom sizes. This is perfect for decades of sliding crossed nan ice, because bigger mineral grains are much apt to get plucked retired by nan ice, leaving holes successful nan aboveground that could origin unpredictable behavior. Blue hone is besides comparatively nonporous, which intends h2o from nan crystal is little apt to get successful and origin fractures.

Ailsa Craig, a distant volcanic land located successful nan Firth of Clyde, disconnected nan westbound seashore of Scotland.

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For nan striking surface, connected nan different hand, “you want to person larger differences successful atom size,” Leung says, because “it prevents definite types of harm from occurring” erstwhile nan stones collide. Ailsa Craig communal green, bluish Trefor and reddish Trefor are each bully for this, which is why they’re utilized for nan main rock; nan striking aboveground is created by carving nan main rock. The rocks for nan 2026 Milano Cortina Winter Olympics will beryllium made of Ailsa Craig communal greenish and usage bluish hone for nan moving surface.

In principle, there’s nary logic stone from different places couldn’t activity for curling. After all, erstwhile that 1890 study was conducted, curlers utilized chromatic from each astir Scotland, nan sport’s birthplace. Ailsa Craig and nan Trefor granite quarry astir apt became nan go-to sources complete clip done immoderate operation of their capacity characteristics, contented and standardization. And blasting is nary longer allowed astatine Ailsa Craig, a now-uninhabited vertebrate sanctuary, truthful different root would thief support curling clubs stocked successful nan future.

This is thing Leung hopes to activity on. An effort successful Canada successful nan 1950s grounded because nan very black, igneous stone called anorthosite that was quarried from Northern Ontario started chipping soon aft use. But pinch amended knowledge of what stone useful best, it mightiness beryllium imaginable to find a caller source. “We could look for rocks that are formed successful a akin situation arsenic Ailsa Craig,” Leung says—maybe Nova Scotia, which is connected nan other broadside of nan Atlantic rifting arena that made nan granitoids recovered successful Ailsa Craig.

He hopes 1 time to activity pinch quarries to get samples to analyze. If he finds immoderate apt candidates, he would emotion to get them made into curling rocks and effort throwing them down nan crystal to spot what happens.