12 MIDDLEMISS: GFOLOGY OF HA7ARA AND BLACK MOUNTAIN. 



means of recognising horizons among it have been discovered. The 

 most prominent band occurring in the slates is especially well devel- 

 oped near Lungurial, and it may be called the Lungurial band for 

 future reference. It is a concretionary limestone) extremely hard, very 

 impure, and of a dark blue-grey colour. The parts of the matrix 

 which wrap round the concretions have resisted weathering more 

 than the concretions themselves, so that they stand out on the 

 exposed surfaces as a pale rusty ochre or dark-brown mesh-work. 

 The rough and pseudo-scoriaceous blocks which thus result are very 

 characteristic of this rock. Another band of calcareous rock ap- 

 pearing among the slates is found quite near to the last, and is of a 

 flesh-white or reddish colour, and marble-like texture. In some 

 places it becomes very much brecciated. I have referred above to 

 the graphitic layers which occur among the slates where they are 

 becoming slightly schistose, as in the Gundgurh range and elsewhere. 

 They appear intimately connected with some of the interbedded 

 limestones, and some of the latter are also impregnated with carbona- 

 ceous material. They will be more fully described in connection 

 with the metamorphic rocks. 



Although there is no other petrological term that would express 



the characters of these rocks except the word 

 Structure of the slates. . . u 



slate, it is nevertheless true that anything in the 



shape of a good slate, using the word in its economic sense, is practi- 

 cally unknown. Nowhere does the rock split up into fine leaves or 

 folia suitable for roofing purposes. On the contrary, although the 

 rock has undoubtedly been cleaved, sometimes across, and sometimes 

 with the bedding, so that it is a slate in the sense of being an argil- 

 laceous rock which owes its fissibility, not to original bedding, but to 

 subsequent re-arrangement of the particles by pressure, yet this 

 arrangement is not perfect enough, nor is the rock pure enough for 

 the production of a good slate. Another cause seems to be the fact 

 that the rock has been cleaved in more than one direction, so that 

 a second cleavage, often spoiling and replacing the first, has resulted 

 in the rock assuming a splintery condition. 

 ( 12 ) 



