72 TALCHEER COAL FIELD. 



Two points seem to be established by these sections— ^rsi, that laterite 



is due to the alteration of rocks by surface action ; 

 Inferences. .... 



second, that the source of the iron is extraneous.* 



What that source is, and why the oxide is so partially distributed, it is 



impossible to say, with our present limited knowledge of the rock, as 



regards its comjoosition and mode of occurrence. 



" Kunkur" abounds throughout the alluvium of the district, 



especially when that deposit is spread over 



Kunkur. 



undulating plains. It does not appear ever to 

 rise to any considerable height on the hill sides, &c. It occasionally 

 penetrates the porous beds of the grits, appearing however only to fill up 

 cracks and interstices. In deep alluvium it does not seem to occur. 



Under all circumstances, its segregation or deposition from water 

 containing carbonate of lime in solution is evident. The lime has been 

 in the first instance probably derived from the hornblende and felspar of 

 the metamorphic rocks. 



Along the great faults forming the Northern boundary of the Talcheer 

 basin, there occur at intervals hills formed of a peculiar and hard rock, 

 at each side of which the sandstones appear altered. At first sight this 

 has much the appearance of a trap dyke, but a little examination shows 

 numerous small cavities filled with chalcedonic quartz, and pseudo- 

 morphs of some tabular mineral, possibly of gypsum or sulphate of 

 barytes, abound, facts which clearly establish the aqueous origin of the 

 rock. 



On further examination it appears that the central mass is an 



enormous quartz vein, containing a breccia of the 



^ ""^^^ ' sandstone in which it occurs, and by the infiltration 



of silica into the porous sandstone on its sides a considerable band of 



• That is to say, iu the Orisaa district, and also as far as has been seen near Raneegunge, 

 in the Burdwan field, and at Midnapm-. With regard to the basaltic laterite of Central and 

 Western India, this does not appear so clear, as basalt, which occurs there, is a highly 

 ferruginous rock, quite competent to supiJy irou for laterite by its decomposition. 



