ECONOMIC GEOLOGY. 259 



be found, and they would be very valuable for building or decorative 

 purposes. 



Besides iron, the only metallic ore which occurs in any quantity 



beyond mere traces is an earthy powdery form 

 Manganese. 



of binoxide of manganese, answering nearly to 



" Wad/' found as a product of weathering among the dolomite at Bhim- 

 garh. To what extent it occurs was not determined, as I discovered it 

 only just as I was leaving the place, and had no opportunity of revisit- 

 ing it. If met with in good quantity, it might be useful in the manu- 

 facture of purple glass or as a bleaching material. 



Gold is found in very small quantities in some of the streams 

 flowing into the upper part of the Malprabha, from 

 both sides, through a region occupied by chloritic 

 schists with rather poor hsematite schist intervening. The exact source 

 of the gold supply remains to be determined. The yield is so exceed- 

 ingly small that these streams are now but very rarely visited by the 

 jalgars or gold-washers. Very few quartz veins occur in this region, 

 and none were noticed with a north to south course. A small stream, a 

 little westward of the village of Belowaddi, appears to be the most 

 auriferous, but I failed in getting an appreciable quantity of gold in a 

 number of carefully selected samples of sand and gravels collected in 

 promising places in the bed. 



Oldest Trapjoean Boch. 

 Of the older trappean rocks, i. e., those older than the Kaladgi 

 series, though so largely developed in dykes throughout the gneissic 

 region, but very little use has been made except in one case, namely, in 

 constructing about three-fourths of the piers of the great bridge by 

 which the Madras Eailway crosses the Tungabhadra at Kasapur. The 

 basaltic diorite here used was quarried from the great Bichal Gutt dyke, 

 the largest and most striking member of the Doab series of dykes 

 (see page 57) . The jointing of the rock in the dyke was found very 



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