ON A I'NTQUl': (K"CURF<T<:NCK of M()1.^•I'.I)F..\UM 

 IN NATAT.. 



Bv Alkxandkr Locik di' Toit. B.A., D.Sc, F.(i.S. 



DnriuiJ: the coiirse of the |)ros])ectino^ which took })lacc 5;onie 

 ten years ag-o in the Tllatinibc Valley, a trihntarv of the Um- 

 koniaa? River, in Imj^endhle County. Natal, an occurrence of 

 ores of Molybdenum was noticed in association with the oil- 

 shales, the mineral beiui:^ present not in quartz veins carrvin.sf 

 crystallised Molybdenite— its normal habit — but as an impreg- 

 nation in coarse sandstone belon<^ing- to the Molteno division of 

 the Karroo System and of Upper Triassic a£^e. 



The habit, therefore, is so imusual that a brief account of 

 the ore-body will no doubt be of interest to mineralogists; in- 

 deed, as far as can be judged from a study of the available 

 literature upon the distribution of Molybdenutu ores, this 

 de])osit is imique. 



The precise locality is on the riglit-hand side of the 

 Hlatimbe Valley, and situated just within the area of Crown 

 Land in the angle between the boundaries of the farms Memala 

 and Duart Castle, below the escarpment of the Drakensberg. 



The Sandstone in question is the identical horizon wdiich 

 has been ma}:>]ied continuously from the Stormberg in the 

 Cape, and known as the Indwe Sandstone. It is only t8 feet 

 in thickness here, but its lithological individuality still j^ersists; 

 at the top it is soft, medium-grained and generally with glittering 

 grains of quartz, while the lowest 4 or 5 feet is harder and 

 coarser-grained, carrying small j^ebbles of white or grey vein- 

 quartz sometimes as much as an inch across. The two parts are 

 separated by a slightly uneven surface, along which are lenticles 

 of extremely well laminated black shale set sometiiues sparsely, 

 at other times close together. 



The sandstone stratum rests upon bluish mudstones. which 

 at the adit are bleached to a J^ale tint ; and the sandstone is 

 followed by the oil-shale horizon, which is here of very inferior 

 quality. 



No signs of mineralisation are to be seen in the upper part 

 of the sandstone, which is fully exposed, nor in the thick sand- 

 stone outcrops higher up tlie mountain-side ;' the Molybdenum 

 appears to be confined to the lowest 4 or 5 feet of sandstone and 

 to a distance of outcrop of 20 yards at most — less than that if 

 slight impregnation be disregarded. Along this face of rock the 

 sandstone shows two irregular dark-stained areas, each a couple 

 of yards across; an adit was driven in at this ])oint to a distance 

 of about 200 feet, but the workings were ultimately abandoned. 

 Prospecting had also been carried out with the aid of a diamond 

 drill, boreholes being put into the hillside at various angles to 

 the horizontal ; records of these are j)ublished in the Reports on 

 the Mining Industry of Natal for 1906 and 1907. Only one of 



