Unst is a geologist’s paradise, containing some rare and exotic rocks and minerals displayed in magnificent settings.
In common with most of the rest of Shetland, Unst was created largely during the Caledonian Mountain Building Period and is in two halves, spilt by a major thrust fault running from the Belmont ferry terminal in the south to the hill of Saxa Vord and the granite outcrop at Skaw in the north. Other faults are also present and this movement, vertically as well as horizontally, has brought together a wide range of rocks from far and wide, presenting us with the fascinating array that we have today. However, the two halves of the island remain distinct.
To the west, the hills running up the picturesque Bluemull Sound are composed of the metamorphic gneisses and schists found throughout much of Shetland. Impermeable to water, the ground is covered in the acidic, waterlogged peat so common throughout the Highlands and Islands.
To the east of the fault the rock is much more interesting, being an ophiolite: oceanic crust and mantle thrust up over the land and which, along with that of neighbouring Fetlar, is the finest example in Scotland.
Running up the centre, and forming some of the hills we see today, is a broad band of serpentine – particularly obvious in the quarry at the Belmont ferry terminal. Serpentine is deep ocean crust formed beneath the Iapetus Ocean and thrust up onto continental rocks as it closed. The outstanding Keen of Hamar National Nature Reserve, overlooking Harold’s Wick and Saxa Vord, is the largest outcrop of serpentine debris in Europe and is home to some extremely rare plants, including Edmonston’s chickweed which is found here and nowhere else. See Plants.
In south-east Unst, greenstone can be found, while further north, at the foot of the Keen of Hamar, another member of the ophiolite suite, chromite, was quarried between 1823 and 1873, reopening from 1908 until 1927 and from 1938 until 1944. Although the largest chromite quarry in Britain with a hole up to 100 feet deep, the ore was of poor quality. The extracted rock was crushed at the fascinating Hagdale horse mill and was then shipped south to be used in explosives, metal plating and yellow paint. Serpentine was also quarried to be made into bricks to line furnaces.
Britain’s only working talc quarry (talc was originally serpentine altered by water deep within the crust) is situated at Clibberswick on the north side of Harold’s Wick, the talc being used as an industrial lubricant. Steatite (soapstone), is composed mainly of talc and was used by the Vikings – and earlier peoples – to make bowls and other utensils. Viking quarrying marks can still be seen at Clibberswick.
Finally, there is gold in them thar hills… well traces of it, along with platinum, palladium and copper, and garnets can also be found.
Read much more at the Shetland Landscapes website.