Tuesday, April 2, 2013

Ancient Volcano for Sale: $2.3 million o.n.o.

For a mere £1.5 million you could be the proud owner of Ailsa Craig, a magnificent but rather solitary island set between Scotland and Ireland in the Firth of Clyde. This noble rock comprises around 90 hectares (220 acres) and today is home to gannets and puffins. In the 16th century the Hamilton family built a castle on the island, to defend it from pirates and the threat of Spanish invasion. Later in its history it was used as a prison, but now the castle lies in ruins and the island is leased as a bird sanctuary. In its current state it would suit a self-sufficient eco-warrior, with no mains electricity, gas, water or telephone connections.

Ailsa Craig’s geological history accounts for its modest industrial relevance. Standing 330m tall in the grey seas of the Atlantic margin, the island is the remnant of an ancient volcanic plug. It is almost entirely made of a microgranite, formed around 62 million years ago during the opening of the North Atlantic, as North America and Europe began their slow separation. Paleogene (tertiary) igneous intrusions, lava flows and volcanoes gave rise to this and other islands that today skirt Scotland’s western shores … Skye, Mull, Rum. The Ardnamurchan peninsula and Northern Ireland’s flood basalts in Antrim (the Giant’s Causeway) were formed in the same burst of igneous activity.

The microgranite from Ailsa Craig is treasured beyond its geological significance. It is used to make curling stones: its fine and regular texture makes it strong and tough. Watch out for smooth polished lumps of Ailsa Craig gliding across the ice at the next Winter Olympics. The granite contains my favourite mineral … riebeckite, a sodium-rich amphibole with strong blue colours. I’ll talk more about that another time. As far as Ailsa Craig’s rocks are concerned, the riebeckite gives the stone a notable blue hue.

So, if you enjoy the company of seabirds, or simply wish to enjoy the sanctuary of an island retreat (and have the cash to spare) what better place than Ailsa Craig than to spend your days? (N.B. I have no commercial interest in the sale!)

Image: Ailsa Craig viewed from paddle ship Waverley. Credit: Paul Hart (creative commons).



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