OHINEMURI MINES.

New Zealand Herald, Volume LXVI, Issue 20405, 6 November 1929, Page 9

OHINEMURI MINES.

NEW PLANT IN OPERATION.

WORK AT NORTH WAITEKAURI

The stamper-mill and cyanide plant of Ohinemuri Gold and Mines, Limited, at North Waitekauri, has commenced crushing. The plant, wifh ' a Comet gyratory crusher, 20 heads • of stampers and four tube-mills, has a milling capacity of 100 tons daily, and is operated by electrical power.- -Full efficiency is expected to . be attained. .by Monday. An average of 15 heads of stampers is now running and the wliob of the plant was sec in motion - without any mechanical difficulty.. . f .-»- > The oro is broken by. an ordinary gyratory -.rusher before gravitating to fhe stampers by "which it is : further " reduced' in a cyanide- solution through screens varying from 16. to 8 mesh. The coarse sands are tben transmitted lo four, tuber mills for fine grinding.' The discharge fiom these mills passes to four large Dorr classifiers so regulated as to ensure that 96 per cent, of the tailings will pass through a 200-mesh screen. Th& coarser ore is returned .to the tube mills for. finer, grinding and thus circulate between the classifiers until it is so finely'ground as to bo carried' "from the classifrers as slime. \ • • <-: - r-,t

This slime passes on. to. four. Wilfrey. - concentrators, where the coarser particles of sulphide matter are separated from thS general slime and returned to the-tube-mills for finer grinding. The finished ore ... slime from the concentrators .then proceeds to two Dorr thickening tanks.. Tho thickened ore slime then discharges continuously into collecting tanks from which it is transferred to air-operatfid slime agitation.tanks, each about 30ft. in height. The ore-slime, . after being" sub-' jeeted to a three (lays' agitation, flows to a Moore vacuum slime filtering plant-wheiv.-the bullion-bearing solution is extracted . from the slimed ore. The cyanide solution, thus released, is run through the extraction boxes containing zinc shavings upon which the bullion in solution becomes precipitated and is afterwards cleaned up and melted in the ordinary way. . . At the mine stoping is in progress at. points in No. 4, the lowest level, north of the main crosscut, where ore of goad grade is being transported to the mill. Stoping is proceeding, also, on No. 5 level south of the main crosscut at. three separate points, which will provide nil tho ore necessary for the mill. Further points will be prepared so that ore-getting operations will be distributed through tha whole of the mine. Meanwhile, develop- _ ment operations have been hindered through leading stopes being carried on the main underground trams. Hie mam drive south at No. 3 level, at a point 2407 ft. from the main crosscut, is in pay- . , able ore for the full width of the drive. This development is in virgin country _ with 600 ft. overhead.