ECONOMIC GEOLOGY. 293 



All the other ores observed seem to have been the result of sol- 

 fataric action. All the rocks older than the 



Ores occurring in veins. „.-,., . 



Siwaliks, whether they be intrusive or sedi- 

 mentary, are frequently traversed by dykes of basalt. In 

 many cases the felspars in these basalts are pseudomorphs con- 

 sisting of calcite, and the alteration has extended to the surrounding 

 rocks with the development of various secondary minerals such as 

 epidote. Sometimes the alteration has proceeded further with the 

 formation of bright coloured metallic ochres and the deposition of 

 specular iron in fissures surrounding the dykes. Lastly, the ores are 

 found in fissures without any igneous rock, constituting real veins, 

 but they always occur in the neighbourhood of the basaltic dykes. 

 The hills called Drana Koh (Lat. 29 15', Long. 6i° 47') in the 



neigl bourhood of Zeh consist of intrusive quartz 



Drana Koh. ... t 1 u- i 1 ,, , ,, . 



dionte. Later basaltic dykes run through this 

 igneous mass ; the intrusion of these basaltic dykes was accompanied 

 by a considerable discharge of mineral vapours which have altered 

 both the basalt itself and the neighbouring portion of the diorite. 

 Veins varying in width from one foot to three feet run parallel to the 

 dykes and contain minerals which probably resulted from the same 

 solfataric action. These minerals are quartz and silicate of copper 

 or "chrysocolla." The copper ore occurs in small crystals of a tur- 

 quoise blue colour. 



At Saindak, particularly in the hill called Saindak Koh and amongst 



the ranges to the north-east, we find the same 

 Saindak. . . . . 



association 01 basaltic dykes and mineral veins. 

 Only here the rocks traversed by them instead of being intrusive are 

 sedimentary, consisting partly of volcanic tuffs and agglomerates of 

 the flysch period, partly of shales and limestones which contain fossils 

 indicating a middle and upper eocene age. The minerals found in 

 the veins are principally carbonate of lime, sulphide of lead or 

 " galena," and carbonates of copper, the green carbonate or " mala- 

 chite " and the blue carbonate or "azurite". The veins are seldom 

 more than a foot in diameter, and it is only where they are widest 



( "5 ) 



