Ailsa Craig is an uninhabited island off the west coast of Scotland. Formed from the plug of a Paleogene volcano, the landmass reaches over 330 m height and ~ 3 km length, and can easily be seen from the Scottish mainland. The island comprises three types of granite: Ailsa Craig Common Green, Ailsa Craig Red Hone and Ailsa Craig Blue Hone (pictured below). The distinctive colouration of the latter type results from the presence of riebekite and arfvedsonite, two amphiboles rich in sodium and iron.
The island of Ailsa Craig is most famous for being the source of material used to make most of the world’s curling stones. These unusual igneous rocks are particularly prized for their low thermal conductivity, impermeable fabric and relative elasticity, lending the stones unrivaled impact resistance. Watch out for these remarkable granites in Sochi; the stones for this year’s Winter Olympics have already been manufactured in Ayrshire and were shipped to Russia last year.
Left: South end of Ailsa Craig, South Ayrshire, Scotland, as viewed from the air. Right: Ailsa Craig Blue Hone (riebekite microgranite). Both images from the British Geological Survey National Archive of Geological Photographs (P000709 and P521397).
If you’ve ever wondered how curling stones are made (and I’m sure you have), then this video should sate your curiousity.
Simon Kelley
Nice post
Its very fine grained, dificult to see individual grains even in thin section, maybe thats what makes it so good for the curling stones.
We digitised a sample from the Sedgwick museum for the UK virtual microscope
http://www.virtualmicroscope.org/content/riebeckite-microgranite