In this part of the reports the author described the features of the ore treatment in Sweden. Two representative mills were explained; one is the Gold-Silver-Copper-Arsenic-Sulphur mill at Rönnskär on the coast of Bothnia Bay, and the other is the iron concentrator at Grängesberg in Middle Sweden.
The Rönnskär mill treats the auriferous sulphide ores from the Boliden mine. The Boliden ore body was found in 1924 after several years' investigation by the geoelectrical surveying. The mill and smelter at Rönnskär are entirely modern. The production from the various units of the plants during the year 1936 was as follows:-
Gold 5, 102 kg, Silver 18, 298 kg, Copper 6, 746 t, Sulphur 19, 616 t, Pyrite concentrate 38, 090 t and Arsenious acid more than 30, 000 t (exact figure is missing).
The Grängesberg mill treats the bre of own mine. The ore body now in working is a huge bed 1, 400 m long and 90 m (maximum width, av. 40 m) wide, dipping 70°. The ore minerals are magnetite and hematite, assaying 60% Fe and 1% P.
Handpicking, magnetic separation and tabling for concentrating magnetite and hematite and flotation for recovering apatite in gangue material are favourably applied.
Two plants “Södra verket” and “Hüller” are running separately, the former is the old plant having capacity of 190 t/hr, (20 hours per day), the latter was built recently and has capacity of 175 t/hr (10 hours per day). Apatite concentration is.practised in this plant.
Production of ores is as follows:-
Hoisted (tons) Ores (tons)
1936 2, 071, 543.0 1, 416, 544.
1937 2, 250, 000.0 1, 500, 000.0 (estimation)
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