General Geology and Ore-Grade Control at the Sherman Mine, Temagami, Ontario

The Sherman Mine, Temagami, Ontario, is an iron ore pellet operation rated at one million tons per year capacity. Mining is done from three open pits in two bands of Keewatin iron-formation intercalated in a 'greenstone belt' thought to be part of the Archean 'Abitibi Belt'. The bands of iron-formation are tabular and steeply dipping, averaging 75 degrees. The principal ore mineral is magnetite. Blast holes, 1214 inches in diameter, are drilled on 28- foot centers, each hole being sampled and assayed for both total iron and magnetic iron. Concentration tests are made in the laboratory to determine the anticipated concentrate grade. Two classes of ore are recognized - 'liberating' or 'refractory'. Blending is done on iron con. tent, degree of ease of liberation (i.e. grain size) and chunkiness. The latter is important, as primary milling is done in autogenous mills. Actual daily mill results are compared with predicted grade from blast holes, exploration diamond drill holes and pit inspection. Hourly mill samples are analyzed by the X-Ray Fluorescent Analyzer, with emphasis on silica grade. In 1969, the pellet grade was improved from 7 .01 per cent silica natural to 5.50 per cent silica natural.
Keywords: Iron, Iron Lake, Lake Temagami, magnetite, Sherman Mine, Magnetite, Mine, Mines, mining, Ore, Ores
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