Economic deposits of chromite were discovered in Unst, Shetland\ud Islands in the early part of the nineteenth century and extraction\ud continuedi ntermittentlyu ntil exhaustiono f the known near-surface\ud deposits in 1945. Since it is likely that further comparable deposits\ud exist at shallow depth, detailed geophysical smeys employing\ud 2\ud magnetic and electrical methods were carried out over ? km of the area\ud of known mineralisationt o test the feasabilityo f detectinga nd\ud delineatingt hem. Seven of 16 small positive gravity arumaJ.ie&se\ud tested by shallow boreholes but only two were attributed to chromite\ud concentrations.T he gravity anomaliesa t the other borehole sites\ud remain unexplained; they may be due to unidentified variations in bedrock\ud density at depth; they may be\ud of weathering and the thickness of\ud in overburden thickness
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