On the north-west coast of Scotland, the Stoer Group of Torridoniam sandstones are exposed at Stoer Bay. Within the purple sandstone are thin layers believed to have been formed by ancient cyanobacteria making a mat which bound the sediment surface together, as in the famous stromatolites of Australia’s Shark Bay. But you don’t have to go to the wild west of Scotland to see them.
Gentlemen, when next in Town,
Seek out that tower of high renown,
Park Lane’s Hilton (one of many),
And, with your hand-lens, spend a penny.
Around this most luxurious loo
Are algal mats exposed to view
In sections through Precambrian sands.
Examine them – then wash your hands.
