206 Mineralogy of Southern India. 



the localities described by him, I am unable to define the 

 rock to which he intended to apply it, as he seems to have 

 used it for pegmatite when it was very white, and for binary 

 granite when it was too far distant for him to perceive the 

 crystalline structure of the felspar. Dr. Boase (Primary 

 Geology, page 203,) defines the difference between pegmatite 

 and eurite to " be according to the size of the grains ; the 

 former being large and crystalline, the latter, small and 

 intimately blended or actually combined." 



Graphic Granite. 



This rock is rather rare : it occasionally occurs among the 

 porphyritic series. It is a variety of granular quartz porphy- 

 ry, being composed of contorted lamina of quartz embedded 

 in a granular paste of felspar, or in compact felspar. The 

 lamina of quartz are contorted into fantastic shapes, some- 

 thing like the characters of the Nagaree dialect. Dr. 

 Macculloch's definition also applies well to the Indian rock. 

 " The quartz and felspar, which compose it, are aggregated 

 in lengthened parallel prisms. The prismatic structure there- 

 fore is seen in one direction ; while, in the reverse, the pe- 

 culiar appearance, whence the term is derived, becomes visi- 

 ble. That appearance is produced by the cross section of 

 the quartz prisms. These are frequently triangular, occa- 

 sionally hexagonal and flattened ; and in a few rare instances, 

 the two minerals form alternating laminae." 

 Saccharine Felspar. 



The only work in which I have met with this term was in 

 a work called, (1 think) Journal of Popular Science. The 

 name is suggested by the resemblance of the mineral to close- 

 grained loaf sugar. It is soft enough to be scraped with a 

 knife. Fracture : earthy granular ; melts before the blow-pipe. 

 I have not analysed it, and am unable to state whether it 

 contains potash or soda. It occurs in Southern India in the 

 porphyritic series, and found embedded in large masses, di- 



