The quarry was in a belt of serpentine on the island of Unst in which chromite is disseminated. In the quarry the ore is concentrated in a pseudo-vein about 12ft wide. The quarry was 86ft deep after a period of working between 1820-1862 and about 30,000 tons of ore were produced. The working was reopened during the first World War and again in 1937, the last time by Shetland Minerals Ltd who also worked another quarry at Midgarth.