Mull is particularly interesting - used to have a volcano the size of Fuji (centred on present-day Salen) which blew up in one gigantic bang. I know someone who specializes in Mull geology - last Christmas we got a card which was a photo of rocks he'd found on Iona, fragments of the Moon blasted off by meteorite impact.

Somewhere there is a warehouse, called the Core Store when it was in southwest Edinburgh (now the site of an Aldi) which contains all the core samples taken from the North Sea by oil test drilling. Thousands of cylinders of rock a few inches across and about a mile long, so you can take a map reference and a depth and see exactly what they found at that point. One of those rooms that would make for a baffling "what are they doing here?" photo.