212 MOLTENO BEDS 



Molteno beds ; silicified wood is common in some of the 

 sandstones. 



The sandstones of the Molteno beds are quite unlike 

 any that occur in the lower groups of the Karroo system. 

 In general appearance and in the character of the surface 

 to which they give rise, they resemble the Table Moun- 

 tain sandstone more closely than any other in the 

 Colony, but they are coarser in grain and much looser 

 in texture. In most localities the quartz grains are 

 coated with a later deposit of quartz with m>re or less 

 perfect crystalline faces which reflect light well, so that 

 the rock sparkles in sunlight. To such varieties the 

 term "glittering sandstone" has been appropriately 

 given. 



Grains of felspar are abundant in these sandstones, 

 sometimes in such quantity that the rock can almost be 

 termed an arkose. The loose texture of the Molteno 

 sandstone has allowed the felspar to weather consider- 

 ably, and the dull white grains of weathered felspar are 

 always conspicuous constituents of the sandstones, more 

 especially in the finer grained varieties. Bounded or 

 spherical nodules, 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 

 spherical zone about the lumps of decomposed sulphide. 

 The hard shell is thus due to the addition of the hy- 

 drated iron oxides to the cementing material usually 

 sent. 



The glittering sandstones form terraces and flat-topped 



