ARCHAEAN AND PLUTONIC ROCKS 65 



Of the hills forming the north-western extension little need be 

 recorded but that some beds of micaceous rock 



Contact metamor- 



phism along the great are associated with the predominantly hornblen- 

 dic variety. The granitoid rock shows much 

 alteration in contact with the immense quartz runs which form a 

 triple crest to the Siddapan Konda ridge, but unfortunately the change 

 has resulted in the altered rock being seen only in a state of advanced 

 decomposition and unfit for further examination. The quartz rock 

 being quite unused, no quarries exist in which the altered 'rock might 

 be seen in a less advanced state of decomposition. There can, I 

 think, be no doubt but that the quartz runs were irruptive and not 

 segregational in their origin. 



The rocks to the east and south of Alur village, the Kasba of the 

 taluq, are everywhere the hornblendic granitoid, 



Pist&citc veins. 



with much pistacite in veins. 



The veins of pistacite are of all sizes from the merest threads 

 hardly perceptible to the naked eye, permeating the rock in various 

 directions, but generally parallel to some great line of jointing up to 

 veins several inches thick. Occasionally veins some feet in thickness 

 are met with, and Mr. Lake, in his notes, mentions one (occurring a 

 little to the north-west of Molagavalli, about 7 miles east-south-east 

 of Alur) "some scores of yards across," but very ill-exposed, "so 

 that its precise thickness could not be determined ". 



The pistacite is generally of a bright yellowish apple-green and 

 highly crystalline, forming a mineral of great beauty which is further 

 set off when, as is often the case, " the veins are bordered by a zone 

 in which the felspar of the gneiss or granite has been stained dark red " 

 (deep salmon pink). "The colour is deepest close to the epidote 

 and gradually fades away as the distance from the vein increases ". 

 (P. Lake, Notes). Grains of pistacite are frequently scattered 

 through the matrix, but generally in the close vicinity to veins of the 

 mineral. 



To the east and south-east of Alur are some of the largest and most 

 unbroken spreads of black soil in Bellary district. It frequently 

 happens that, for distances of 6 and 7 miles at a stretch, the sub-rock is 



E ( 65 ) 



