Fairy Island aka Ailsa Craig is an island of over 200 acres in the outer Firth of Clyde, 10 miles from mainland Scotland.
Research has shown that the granite on Ailsa Craig has an unusual crystalline composition that has a distinctive appearance but a uniform hardness. This blue hone granite was quarried to make curling stones.
This type of micro-granite with Ailsite (known as Riebeckite) which is used to make stones for the sport of curling. As of 2004, 60 to 70% of all curling stones in use were made from granite from the island and is one of only two sources for all stones in the sport, the other being the Trefor Granite Quarry in Wales. Ailsa Craig produces two types of granite for curling,
Blue Hone and Ailsa Craig Common Green. Blue Hone has very low water absorption, which prevents the action of repeatedly freezing water from eroding the stone. Ailsa Craig Common Green is a lesser quality granite than Blue Hone.
In the past, most curling stones were made from Blue Hone but the quarry is restricted by environmental conditions that exclude blasting. Kays of Scotland has been making curling stones since 1851 and has the exclusive rights to the Ailsa Craig granite, granted by the Marquess of Ailsa.
The now uninhabited island is formed from the volcanic plug of an extinct volcano. It stands out because all younger sedimentary rocks covering Southwest Scotland have long since been eroded away. But the island survived erosion because it is composed of much harder igneous rocks from the Palaeogene era.
The island, colloquially known as “Paddy’s milestone”, was a haven for Catholics during the Scottish Reformation in the 16th century, but is today a bird sanctuary, providing a home for huge numbers of gannets and an increasing number of puffins.