Though they have come in many different varieties and materials over the years, the majority of most modern curling stones are made from a peerless granite quarried on a small Scottish island called Ailsa Craig in the Firth of Clyde. The density and consistency of this granite has made it the ideal choice for curling stones. There are also other types of granite used in today’s curling stones. Each stone is meticulously finished to exacting specifications. It may not exceed 36″ in circumference and 4 1/2″ in height. They weigh approximately 42 pounds each. Each stone has a handle at the top that is usually molded out of plastic or a composite material.
The bottom of the stone is concave, with a flat “running surface” at the outer edge. The sides of the stone are rounded, with the exception of the equator or “strike band”, which has a flattened surface. This flattened surface is the point of contact between two stones and it helps to prevent chipping. The handle of the rocks usually has two numbers on it. One of these numbers correlates to the ice sheet number that the stone belongs to. The other number is the rock’s number. The rocks are played in order by each team, with the “lead” throwing #1 & #2, the “second” throwing #3 & #4, the “third” throwing #5 & #6 and the “skip” throwing #7 & #8. Rocks for each team are usually differentiated by having different colored handles. Modern stones are nearly identical in every aspect allowing for greater consistency and shotmaking. One set of 16 stones for a single sheet costs about $7,000 to $8,000. Fortunately, the club supplies these! Stones usually have a lifespan of 25-30 years before needing to be reconditioned depending on amount of use. Some stones can have a life span of 40-50 years depending on the type of granite used and the type of insert.
Common kinds of Curling Granite
- Blue Hone
- This type of granite is mainly characterized by its color and condition of the strike bands. Light gray with random white specks throughout stone. Blue hone is the optimum material for being used as an insert for repairing running surfaces of pitted stones.
- Ailsa Craig Common Green
- Green in color, Ailsa Craig Common Green stones have large black deposits in the stone that are outlined with white flecks. There is vast difference in the quality of Ailsa Craig Common Green granite. It can be quite good or can have a large amounts of impurities allowing for holes and rapid deterioration of striking bands.
- Red/Brown Trefor
- Red/Brown Trefor can be found in several shades of brown, and will always have white and black flecks that run throughout the stone . Trefor granite is a larger grained granite which leaves it slightly susceptible to pitting in the running surface, but make it excellent material for strike bands.
- Blue Gray Trefor
- Usually deep blue/gray color, blue gray trefor granite has prominent white flecks that can be easily spotted throughout the stone.
- The Keanie name derives from the family name of the company making these stones rather than the proper name of the granite. It is pinkish in color, with large white and black flecks throughout, and is a very porous material.
- Combination of types of granite One type might be used as the stone, while another might be used as the insert for the running surface, or bottom of the stone. (usually Trefor or Keanie with Blue Hone inserts.)