<P> The curling stone ( also sometimes called a rock in North America ) is made of granite and is specified by the World Curling Federation , which requires a weight between 38 and 44 pounds ( 17.24 and 19.96 kg ) , a maximum circumference of 36 inches ( 914.4 mm ) and a minimum height of 4.5 inches ( 114.3 mm ) . The only part of the stone in contact with the ice is the running surface , a narrow , flat annulus or ring , 0.25 to 0.50 inches ( 6.4 to 12.7 mm ) wide and about 5 inches ( 130 mm ) in diameter ; the sides of the stone bulge convex down to the ring and the inside of the ring is hollowed concave to clear the ice . This concave bottom was first proposed by J.S. Russell of Toronto , Ontario , Canada sometime after 1870 , and was subsequently adopted by Scottish stone manufacturer Andrew Kay . </P>
<P> The curling stone ( also sometimes called a rock in North America ) is made of granite and is specified by the World Curling Federation , which requires a weight between 38 and 44 pounds ( 17.24 and 19.96 kg ) , a maximum circumference of 36 inches ( 914.4 mm ) and a minimum height of 4.5 inches ( 114.3 mm ) . The only part of the stone in contact with the ice is the running surface , a narrow , flat annulus or ring , 0.25 to 0.50 inches ( 6.4 to 12.7 mm ) wide and about 5 inches ( 130 mm ) in diameter ; the sides of the stone bulge convex down to the ring and the inside of the ring is hollowed concave to clear the ice . This concave bottom was first proposed by J.S. Russell of Toronto , Ontario , Canada sometime after 1870 , and was subsequently adopted by Scottish stone manufacturer Andrew Kay . </P>
how heavy are the stones in olympic curling
how heavy are the stones in olympic curling
between 38 and 44 pounds ( 17.24 and 19.96 kg )
between 38 and 44 pounds ( 17.24 and 19.96 kg )