172 FOOTE: GEOLOGY OF THE BELLARY DISTRICT. 



In point of thickness and of the height of the ridges they form, 



_. . .. . they exceed the average trap dykes consider- 



Their dimensions. * ° r ' 



ably, but in comparative length they are much 

 inferior to them. 



They are probably all older than the great dyke series, but in only 

 m , . one single case was a contact between them met 



Their age. 



with, and in this case the trap dyke had unques- 

 tionably cut through the quartz-run, and is now seen to include 

 numerous fragments of it. This is to be seen in the second great 

 quartz-run north- north-east of Harappanahalli above {vide above, 

 page 168). 



In all 84 of these quartz-runs were mapped, and may be 

 Their number and ref erred ™ u g h ly ^ 1 4 groups, which are however 

 grouping. simply directional and in no way geographi- 



cal. 

 The almost entire absence of accessory minerals from the quartz- 

 Accessory minerals runs is ver y remarkable, and in only two cases 

 wantin S- were any indications of an included metallic 



mineral observed. This was in both cases copper in the form of 

 green carbonate. Inclusions of small pink felspar crystals were 

 also observed in a solitary case, and in the same run in which one 

 of the two copper shows was noted. This will be referred to again 

 further on (page 175). 



The other case in which copper carbonate was seen is that of an 

 „ , important run about a mile north-north-west of 



Occurrence of copper, 

 north of Haroppana- Harappanahalli (Hurpunhully), which place is 



quite a centre for great quartz-runs. In this case 



the carbonate occurs in the forms of films, often of extreme thinness, 



or small veinlets, coating many joint planes and lining innumerable 



cracks in the veinstone. The ore is an earthy-looking malachite 



and old workings for it remain, and will be referred to in the chapter 



on Economic Geology (page 197). 



It is this same run which is cut by a great trap dyke as described 



above (page 168). No connection seems to exist between the 



( 172 ) 



