Manganese Poisoning in Moroccan Miners

Abstract

MEDICINEtons in 1922 it reached by 1953 420,000 tons, of which 40,000 tons are chemical salts.The mines of Imini, Bou-Arfa, and Tiouine (in order of importance) furnish 90% of Moroccan production.Geologically the deposits of manganese in Morocco are of two principal types, sedimentary deposits and seam deposits.The first are the more important and make up the greater part of the country's production.They are situated in cretaceous terrains such as Imini and Talsdremt, liassic as at Bou-Arfa, or cambrian as at Tiouine (Rodier, 1950).Reserves of these deposits would amount to 15,000,000 tons. ExploitationThe techniques vary in different mines.Most of the workings at Imini are underground.The friable and powdery nature of the ore only very rarely calls for blasting or the use of rock-drilling machines.Formerly excavation was by hand-pick but now hand-picks have been replaced by pneu- matic drills.The ore is removed in tubs winchhoisted up an incline.One part only is worked as open-cast.The mineral extracted is made up of pyrolusite very rich in manganese.Formerly the ore was screened and hand-picked but now this process is replaced by pneumatic washing.The inconvenience of this system is to get rid of the quantities of dust so it has been necessary to add to this an elaborate apparatus, which seems satisfactory, for suppressing the dust.The powdery nature of the ore renders its transport difficult and is a serious handicap to its use in blast furnaces.It is thus necessary to treat it in Casablanca in a " sinterization" works using a Dwight-Lloyd machine.At Bou-Arfa working is by horizontal terraced trenches.The general character of the ore is rather friable and as much as a third of production is made up of small stuff.At Tiouine workings are entirely underground and mined by the gallery-and-pillar method.Because of the hardness of the rock, excavation is by blasting after the blast holes have been bored by rock drills.The spoil is removed by mine tubs on the level, which are subsequently pulled to the surface by electric winches.Sorting of the large blocks of ore is done by hand-picking.