Yol. 56.] THE GEOLOGY OF G1LGIT. 347 



and devoid of pleochroism in transmitted light. A single cleavage 

 runniug parallel with the length of the grains or prisms is common, 

 and this is interrupted, or crossed, by a set of cracks approximately 

 at right angles to the first set. In some respects the mineral is 

 suggestive of colourless epidote, and in others of white pyroxene. 

 It is often difficult to distinguish the one mineral from the other, 

 and in this case the difficulty is unusually great. I have decided in 

 favour of pyroxene, for two reasons : firstly, because sections showing 

 cross-cleavage exhibit an oblique emergence of an optic axis which 

 is not seen in sections of epidote or zoisite showing cross-cleavage ; 

 and secondly, because the refraction of the mineral, though high, is 

 lower than that required for epidote. I tested a considerable number 

 of fragments, and in every case the refraction came out less than 

 1 *740. The refraction would do for zoisite, but the double refraction 

 of the mineral under consideration is far too high for that mineral. 

 On the whole, I conclude that the mineral is pyroxene, and that 

 the difficulty in its diagnosis arises from the fact that the first stages 

 of alteration to a member of the epidote-zoisite family had set in. 1 



The pyroxenite just described is cut through by dykes and veins 

 of the Askurdas Muscovite-Granite (see p. 343). 



On the way from Ramghat to the Lecher River, a little before the 

 pyroxenite is reached, and at the place marked on the sketch-map 

 (p. 344), the hill-sides are covered with the debris of a great landslip 

 which in 1841 completely blocked the Indus and caused a disastrous 

 flood in the plains of the Panjab. The debris consist of a diorite 

 which is a holocrystalline mixture of hornblende and plagioclase, 

 with magnetite and garnet as accessory minerals. The hornblende 

 is of a dull brownish-green in transmitted light ; it is feebly pleo- 

 chroic in pale bluish-green and yellowish-green tints. A little 

 of the plagioclase is visibly twinned, but it has the granular habit of 

 quartz. It is full of microliths and globular inclusions which are 

 probably micro-garnets. There are also gaseous and liquid inclusions 

 with moving bubbles. 



With this diorite is associated the acid variety of the Hatu 

 Pir Granite. Viewed macroscopically it is a platy, sheared- 

 looking rock. Under the microscope it gives good examples of 

 amoeboid structure. 



Both the diorite and the acid granite had fallen down in large 

 masses from high cliffs above the horizon of the Hatu Pir Granite, 

 which is in force, as already mentioned, on both sides of the river 

 between Rampore and Julipar. The cliffs being inaccessible, my son 

 could not see whether the acid variety of the Hatu Pir Granite was 

 intrusive in the diorite or whether the diorite had intruded into the 

 granite. 



Eetween Bonar and Chilas a hornblende-gabbro is common. 



1 The setting-up of such a change in an aluminous pyroxene such aa 

 leucaugite seems quite possible. Epidote on fusion yields lime-augite and 

 anorthite [F. W. Clarke, ' Constitution of the Silicates' Bull. U.S. Geol. Surv. 

 No. 125 (1 895) p. 30] ; and the conversion of augite through chlorite into epidote 

 has already been recognized (C. R. Van Hise, 'Principles of N. American Pre- 

 Cambr. Geol.' 16th Ann. Rep. U.S. Geol. Surv. (1894-95) pt. i, p. 690]. 



