The area's other major rocks are Torridon sandstone, Cambrian quartzite and Durness limestone.  Torridon sandstone is a sandy, layered, sedimentary rock sometimes looking like concrete.  The distinctive mountains of Cul Mor, Suilven, Canisp and Quinag are huge masses of Torridon sandstone capped with quartzite.  Arkle is largely composed of Cambrian quartzite.  Limestone forms the steep slopes of Knockan as well as the limestone pavements, underground water systems and caves at Inchnadamph.  These rocks date from a time when this part of Sutherland was attached to North America and the rest of Britain was yet to join it.  The world famous and much studied Moine Thrust Fault is visible here.  More 'recently', the effects of the Ice Age have left a spectacular scraped landscape of deeply-gouged glens, myriad lochans, dramatic coastal fjords (such as Loch Inchard) and bold mountains (such as Foinaven and Arkle).

Between Laxford and Rhiconich, the building of the new road has exposed folded patterns in the Lewisian gneiss rocks.  The original horizontal layers have become twisted, broken and folded through the intense pressure and movements of the earth's crust.

Knockan Crag, situated just south of Elphin near the border of Sutherland with Ross-shire, is one of the most important sites in the Scotland for understanding how the landscape of northern Britain was formed.  The crag shows an unusual situation where older Moine rocks have come to lie over much younger Durness limestone.  Situated there is an exhibition about the landscape and geology of the area, and two circular trails for walking.   It was at Knockan that the prominent Scottish geologists Ben Peach and John Horne first identified fault lines, and a memorial beside Loch Assynt recognises their pioneering work.