26 MIDDLEMISS: GEOLOGY OF HAZARA AND BLACK MOUNTAIN. 



most probably originally was a rhyolitic flow. At all events under 

 the microscope it shews the fine-grained appearance of a microfelsitic 

 ground-mass without any porphyritic crystals of orthoclase or quartz, 

 or any other characteristic mineral or structure, — eg., spherulitic or 

 perlitic. Occasionally there is an indefinite wavy structure as if the 

 remains of flow-structure, accompanied by a fibrous green mineral 

 with strong double refraction running through the rock. At the 

 bottom of this volcanic stage we have some very siliceous beds of 

 grey and white colours, which seem to be of the nature of chert or 

 some other amorphous form of silica, and to have been formed 

 just as the chert bands in the upper parts of the Infra-Trias 

 limestone were formed by the contact metamorphism of the felsitic 

 flow on the limestone. Above this, on the north face of Sirban, come 

 pink and white and greenish coloured felsitic rocks, banded in these 

 colours, very tough to the hammer, with rough surfaces, and 

 frequently exhibiting an appearance due, I think, to brecciation, a 

 brecciation that has taken place as the material of the flow half 

 solidified and then went on again. Some buff coloured, sometimes 

 purplish, and micaceous shales follow above these, and then comes 

 an earthy concretionary or pisolitic haematite associated with broken- 

 up material from the felsitic rocks below. Some of this develops 

 into a band 5 or 6 ft. thick of good earthy haematite, which would be 

 useful economically if the coal of the neighbourhood should ever be 

 successfully worked. A few quartzites occur here and there at 

 uncertain horizons among these volcanic beds. 



The thickness of this volcanic stage is not very great, never ex- 

 ceeding 50—100 feet. In the southern parts of the slate zone the vol- 

 canics are only represented by white saccharoid quartzites and 

 sometimes by an arkose. 



Waagen and Wynne failed to recognise the volcanic nature of 

 some of this stage, and indeed expressed disbelief in its occurrence, 

 as mentioned by Dr. Verchere. In a foot-note 1 referring to rocks 



1 Mem. G. S. of I, Vol. IX, 1872, Art. 3, p. 6 and p. 14. 

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