Show S vi 5 W undercurrents Under currents for platinum and flour gold X j WRITTEN FOR THE MINING REVIEW 5 J a a a a a e much of the placer ground of the pacific coast carries from ten to twenty per cent of its values in flour or fine gold these values associate themselves very closely with the black sand and frequently in connection with platinum and the five metals of the platinum group because of the lightness of the sands and the fineness and flakiness of the values it is a difficult matter in truth almost an utter impossibility to save them by the ordinary methods of riffle and sluice for that reason many surface gold miners lose from ten to twenty and sometimes a greater per cent of the values of their diggings because of the failure to save the flour gold and sands A number of methods for saving flour gold have been tried in western placer mines these methods have ranged all the way from a series of grizzlies grizzlier grizz lies to hungarian Hunga flan riffles fiffles and sluices but in most cases the arrangement has been too coarse or too crude for the handling of the deli delicate caie and slippery particles the best method the writer has ever seen employed in the catching and saving of flour gold Is that of a system of rents the requisites and the principles of this system are simple and can be built installed and operated by any mine foreman the accompanying illustration is from a photo of one of the undercurrents under currents in use at the royal group hydraulic mines of galice district southern oregon the system was the result of considerable study by mana ger john harvey of these mines and many other miners have been induced to adopt the same method of saving their flour gold values the undercurrents under currents two in number are built one on either side of the main sluice out near the dump they should be built near the end of the sluice that the riffles fiffles may have an opportunity to catch all the gold possible before entering the undercurrents under currents A grizzly made of one half inch stamp iron bars three or four inches wide are set edgewise three quarters of an inch apart on the bottom of the sluice the grizzly should have a length of five feet and a width equal to the width of the sluice beneath the grizzly is placed a cross sluice into which the water empties when it pours K aa 4 4 A r NV h 4 wa M 1 sluice of royal group hydraulic aines southern oregon through the apertures aper tures and flows each way to be evenly distributed over broad riffle tables which are the undercurrents under currents proper one of these is shown in the foreground of the illustration by the time the grizzly or the end of the main sluice is reached the black sand with its close associates flour gold and platinum has settled well down to the bottom of the sluices and drifts along close over the riffles fiffles by the flow of the water ordinarily these values keep drifting and flow on off over the dump but in the case cage of the undercurrent they are drawn down through the grizzly and are out over the broad riffle tables on which they settle the tables should be about ten feet wide and twelve feet long with a drop of about eight or ten i inches just enough to td allow aldow a smooth and even flow of the mass ol of water and sand over the riffles fiffles rif fles tb rif fles fies are made by building the floor of the tables of two by four planks set edgewise eve every ry alternate plank being dropped down one half or three quarters of an inch another way of building the tables is by making them smooth or laying the boards of the floor close and covering it with heavy burlap this is most favored by mining men as the burlay can be easily lifted and dipped in vats for cleaning it is also easily and cheaply replaced the flow of water over the riffle tables is regulated by gates on the side of the main sluice under the grizzly the amount of flow can only be regulated by trials and tests but the miner will find that a certain amount of flow neither too great nor too small is necessary to attain the best results the gates are also convenient in that one of them can be shut off when it is desired to clean one of the tables in this way there is no loss |