Some of the best granite in the world is in Scotland. The highlands are very rocky and sit upon a fault (the Highland Boundary Fault), which creates the craggy mountains and deep lochs. The highlands are also replete with gneiss, schist, and sandstone. Also, some of the oldest rocks in Europe come from the Outer Hebrides, including Torridonian Sandstones which can be as old as 3 billion years. This is why Scotland has produced many great geologists, like James Hutton, the father of modern geology.

...sorry, I just completed a geology class.