Red sandstone, NW Scotland

Image to left: Red sandstone hand specimen from NW Scotland

The Lewisian gneiss (hand specimen to right), a metamorphic rock whose history goes back almost 3000 million years, now forms the low land around the mountain, Suilven.

The rocks on top are layers of red sandstone & conglomerate. These show that rivers flowed across the ancient landscape of eroded metamorphic rocks around 1000 million years ago, depositing sands and gravels.

More recent erosion, by ice sheets and rivers, has uncovered much of that ancient landscape, leaving isolated sandstone hills like this one.