Ailsa Craig

Ailsa Craig is an island of 99 ha in the outer Firth of Clyde, 16 km west of mainland Scotland, upon which microgranite has long been quarried to make curling stones. The now-uninhabited island comprises the remains of a magmatic pluton formed during the same period of igneous activity as magmatic rocks on the nearby Isle of Arran.

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.

Source: Wikipedia