An Sgurr --- the glass mountain!

The Sgurr of Eigg is iconic, it towers over the island like a giant watching everything that happens in the community around it, and looking as though it is ready to pounce if it detects any misdemeanours.  It was formed 59 million  years ago , at the same time as the island of Rum, when the Atlantic was opening up and there was a lot of volcanic activity in what is now the Inner Hebrides. It is made of glass! Not clear glass, of course, it looks like ordinary rock to the untrained eye, but it was a river of lava flowing down a valley that solidified into a structure, called pitchstone, that is technically a glass. Once solid it was very hard and was left as this prominent ridge as the surrounding basalt was worn away. The extra is a more detailed view of the Sgurr.