TORRIDONIAN SANDSTONE

WHAT IS IT? A group of red and brown sandstones and shale found up the northwest coast of Scotland. It lies in distinctive horizontal strata, seen most clearly in Applecross and Torridon and spectacularly on Liathach and Beinn Alligin.

WHERE? From the Isle of Rum in the south, along the Sleat peninsula of Skye and north along the mainland from Applecross to Durness. It’s divided into three subcategories – the Stoer group, which is the oldest, and the Sleat and Torridon groups. See The Old Man of Stoer, Suilven and the hills encapsulating the Bealach na Ba.

HOW SLIPPY? Not very. A reliably grippy rock. AND ANOTHER THING The earliest signs of life found anywhere in Europe, primitive single-celled algal organisms called stromatolites, occur in Torridonian sandstone near Lochinver.