580 million years ago the schist and pelite rocks at Garths Ness were forming as sediments on the margin of an ancient ocean. ?Heat from molten magma deep beneath the sea floor caused superheated seawater to circulate through the crust, dissolving minerals, including copper and iron, from the surrounding rocks. When the mineral-rich water spewed from hydrothermal vents on the seabed it cooled rapidly and the minerals precipitated, forming black chimney-like structures called black smokers. The minerals eventually formed massive ore deposits in the form of mounds within the sea-bed sediments. Ore deposits like these can contain economic concentrations of copper, zinc, lead, barite and gold. ?The massive ore deposit here at Garths Ness contains mostly iron sulphide (pyrrhotite) with some copper?iron sulphide (chalcopyrite). It was mined briefly around 1800 by Alexander Crighton and Andrew Grieson, Laird of Quendale who hoped to win profitable amounts of copper. The venture proved uneconomic but for a while the laird was tricked into continuing working by resourceful workers who hid copper pennies in the assay samples to make the ore appear richer!
The massive ore deposit which can be seen at Garths Ness was formed from minerals deposited from a Black Smoker - a stream of superheated water that erupts from beneath the seabed.
Directions
Garths Ness is one of the southern tips of the Shetland Mainland
Take the A970 and turn off to Quendale
Continue until the turning to Quendale Water Mill and turn left
Continue until you reach the disused military buildings at the very end of the road and park (open gates as necessary but please leave them as you found them)
Walk down the hill along the line of the fence and then head around the coast to the right
The site is situated in a small inlet and can be viewed from above