Fauna and Stratigraphy of the Stormberg Series. 



les, hollowed out in the centre when the hard outer shell has been 

 broken through, are quite a characteristic feature of the Molteno 

 sandstones. The nodules are formed by the oxidation of pyrites and 

 the deposition of some of the resulting iron compounds in a spheri- 

 cal zone about the lumps of decomposed sulphide. The hard shell 

 is thus due to the addition of the hydrated iron oxides to the 

 cementing material usually present. 



The lowest of the coarse glittering sandstones has been termed 

 the "Indwe Sandstone", and forms a reliable bench-mark from 

 which the horizons of the different coal outcrops can be delined. 



The liner grained varieties of sandstone .... are of a yellowish 

 grey or cream colour and furnish a good building stone. 



The coarse gritty sandstones occasionally become conglomeratic, 

 the pebbles consisting principally of vein-quartz and of quartzite. 



A peculiar feature is the occurrence in the Molteno sandstones of 

 smooth rounded or oval pebbles usually a few inches across but 

 occasionally ranging up to boulders a couple of feet in diameter. 

 They are, as a rule, scattered irregularly through the sandstones, 

 but in the Molteno Division they are particularly abundant along a 

 certain horizon and form a bed of conglomerate a few feet in 

 thickness. The pebhles are sometimes found resting upon a coal 

 seam and partly imbedded in the base of the sandstone overlying 

 the coal. The pebbles are almost entirely of white or brownish, 

 sometimes glassy, quartzites like those of the Witteberg or Table 

 Mountain series. They are most abundant to the south-west of the 

 Stormbergen. Some of these pebbles show pitting externally due 

 to the formation of cubes of pyrites a layer of which occurs just 

 below the surface. 



In the Molteno Beds there are numerous outcrops of coal, but 

 the workable seams are restricted to three well-delined horizons. 

 The lowest one is that of the Indwe seam; to this belong the coals 

 at Indwe, Cala and that near Engcobo. The second is about eighty 

 feet higher and is known as the Guba seam. The uppermost is the 

 horizon of the Molteno seam, 300 ft. above the Indwe seam. 



The layers of coal seldom exceed twelve inches in thickness (in 

 the Guba seam there is one about 25 inches thick), but as several 

 usually occur alternating with thin bands of black shale it is pos- 

 sible to extract from three to four feet of coal in mining operations. 



On all three horizons these composite seams appear to occupy a 

 number of detached areas, in between which the coal is either 

 replaced by shale or else is entirely absent. In most cases this is 

 due to non-deposition of carbonaceous material, but sometimes to 



