Perhaps the most interesting piece of equipment used in curling is the curling stone that is the center of all the action. Most curlers are aware that the stones are made of granite and that the World Curling Federation mandates they weigh between 38-44 pounds, but not many are aware of the very unique island where the rocks originate or all of the unique features that make a curling stone special.
Off the coast of Western Scotland lies an island called Ailsa Craig. It is quite a small island, measuring just 0.38 of a square miles in area with zero official inhabitants (save birds). But this island is the birthplace of approximately 65% of all the curling stones produced in the world. The reason for this is Ailsa Craig contains two very specific types of granite, Blue Hone and Ailsa Craig Common Green. There are a few important aspects of these types of granite that make these rocks perfect for curling.
First, they absorb water at a very low rate. This is obviously important since most of a curling stone’s life is spent on a sheet of ice, which often times is melting beneath the weight of the stone. Most curlers have experienced picking up a stone at the beginning of a game that has begun to partially melt into the ice surface because it may have been stored off-ice and correspondingly arrives on the ice at a high temperature. It is imperative that the stome not absorb any of the water it sits in so the stone can travel on a predictable path.
Second, the geodynamics of these types of granite make the stones more resilient than other forms of granite. The internal crystals of Ailsa Craig granite fit together in a very tight pattern which lends to increased strength and resilience. This is vital for a curling stone that will spend decades being bombarded by other curling stones at high speeds.
Third, Ailsa Craig granite granite has a very favorable sliding profile. As curlers are aware, only a thin band on the bottom of the stone (called the running band) makes contact with the ice during play. When a stone is constructed, small scratches and grooves are built into the running bands so as to make the stone both slide and curl better. These special grooves are particularly effective in granite from Alisa Craig, allowing more predictable shots and better speed control than with other types of granite.
A final benefit is one that is purely aesthetic. Both forms of Ailsa Craig granite, blue hone and common green, contain some rare minerals that give the granite a blue-green appearance with speckles that other types of granite do not contain. Correspondingly, other types of granite have a visual appearance more on the solid gray variety that most curlers would vote not as visually appealing.
The island of Ailsa Craig and its granite are not the only producers of curling stones in the world; however, their market share speaks for itself for a reason. Another voice in the corner of Ailsa Craig granite curling stones is the International Olympic Committee. In fact, Ailsa Craig curling stones have been used in every single Olympic curling event in history. As a final interesting point, the entire island of Ailsa Craig is currently up for sale. It is owned by a member of the Scottish royal family and has been on the market since 2011. The asking price is a mere 1.5 million pounds which is around $2.5 million US dollars. Seems like quite a deal to own such a piece of both curling’s history and future.