15^ MOLVr.DEXUM IN N'ATAL. 



because it contains a small amount of molybdenum, thouj^h bow 

 this is combined has not been ascertained. 



As regards the genesis of the deposit, no definite suggestions 

 can be made, unfortunately. As far as can be judged, the black 

 molybdenum bearing part of the sandstone is irregular in shape, 

 and in places fairly shar])ly defined from the rest of the rock. 



The molybdenum compounds could not have been of detrital 

 origin, for then the deposit would gradually fade away into barren 

 sandstone on either side ; also the quartz pebbles, when broken, 

 are free from enclosed flakes of molybdenite. The presence of 

 pyrite and marcasite is common indeed in the Indwe Sandstone, 

 'but the amount present here is much higher than usual, and a 

 great part of the sulphides of iron must therefore have been in- 

 troduced later, probably along with the molybdenite. 



Several such nodules from this sandstone at diiTerent locali- 

 ties in the Cape Province gave no indications of molybdenum 

 when tested by the delicate reaction with stannous chloride. 



The source of the carbonaceous matter is another difficult 

 prol)lem ; its restriction to the ore-body will hardlv allow of its 

 being an original constituent, but on the other hand it is not vola- 

 tile. In some ways it recalls the odd anthracitic " coals " found 

 in irregular veins and fissures in the Western Karroo. 



There are no signs of any chamiels up which ascending solu- 

 tions could have made their way. and there are no dykes in close 

 proximity. The only igneous intrusion is a nearly horizontal sill of 

 dolerite, which crops out at a level fully lOO feet above the occur- 

 rence, and which might have been concerned in its genesis. This is 

 not at all unlikely, for small amounts of iron and occasionally cop- 

 per pyrites are found in these intrusions in the Karroo Sy.stem ; in 

 the Insizwa Range, in Mount Ayliff, there is a good deal of nickel 

 as well (in the form of sulphide) along with pyrrhotite. 



This sporadic occurrence of molybdenum in Natal may 

 quite well l)e genetically connected with the intrusion of the 

 Karroo dolerites, but it is only fair to j)oint out that prospecting 

 has not l)rought to light any similar mineralisation at points a few 

 miles away, where the sandstone has been cut through by the 

 dolerite sheet in question. 



Meteoric Stones. — Or. (j. T. Trior. Kee])er of the 



Mineral Department of the British Museum, has contributed to 

 the Transactions of the Mineralogical Society a paj:)er on 

 some meteoric stones, including those which fell at Kroonstad, 

 Orange Free State, on 19th November, 1877, and at 

 Daniel's Kuil, (lri(|ualand West, on 20th March, 1868. Both 

 these meteorites were analysed, and their mineral composition de- 

 duced from the results. The Kroonstad stone seemed to con- 

 .sist mainlv of bronzite, olivine, and nickel-iron, the percentages 

 being respectively 35.03, 29.44, and 18.49. The Daniel's Kuil 

 meteorite showed 55.76 per cent, of enstatite and 25.45 per cent, 

 of nickel-iron. 



