102 Notes on Geological Specimens from [Feb. 



known by the name of" black granite," and forms, when finely polish- 

 ed, the beautiful tombstones of the Golconda mausoleums, and the 

 pillars of that in which Hyder and Tippu Sultan are deposited, at 

 Seringapatam. The remarkable quartz veins in the neighbourhood of 

 Hyderabad have been described by Voysey and Christie ; it is there- 

 fore only necessary to mention, that they occasionally exhibit a more 

 or less regular crystallization, and at the same time, acquire the fine 

 tints of the amethyst. It is seldom that they are sufficiently regular 

 and perfect for the purposes of the lapidary ; such specimens were, 

 however, discovered a few years ago, close to the European barracks, 

 and at a little distance from a great greenstone dyke, but not in direct 

 contact with the quartz bed containing the crystals, which, on the 

 contrary, passes into the ordinary sienitic granite of the country. The 

 colour of the amethystine quartz seems to be derived from magnetic iron 

 ore, which is disseminated in grains both through the milky quartz 

 and the granite, amongst which they are found, and has not been noticed 

 elsewhere in the neighbourhood. The amethystine quartz was again 

 met with 60 miles north of Secunderabad, near Bekanurpettah, in loose 

 masses, along with that variety of laterite found near Beder, and 

 described by Voysey, and which is seen along the coasts of Malabar 

 and at Boranghur in the Southern Concan resting on basalt. The rising 

 ground on which they were found is composed of granite ; but the 

 country around is of a black trap soil, and numerous low flat ranges 

 of basaltic hills are seen to the north, the east, and the west. A vein 

 of white quartz is also met with as at Secunderabad, but the specimens 

 differ, in containing irregular shaped geodes of agate, lined with crys- 

 tals, or a red opake mamillary quartz, approaching to calcedony. The 

 iron in these is usually imperfectly mixed with the quartz, and from 

 the appearances above described, and the quartz having in several 

 specimens been changed into a red jasper, the surrounding trap may 

 be supposed to have altered the rocks. The colouring matter seems 

 to have been afforded by the laterite, which is found in the neighbour- 

 hood apparently in dykes, and in contact with the quartz which inter- 

 sects the granite : but there being no section, and the water- worn 

 surface only being visible, no evidence could here be obtained, in 

 support of any of the opinions entertained by geologists, relative to 

 this singular formation. The amethysts are also found south of Jan- 

 ganapilly, and at Kamareddypettah, and Mr. W. Geddes met with 

 them, of a greenish yellow tinge, south of Balcondah. 



Granite Tract between Hyderabad and the Nirmul Hills. 

 The valleys and some plains about Bekanurpettah are composed of 

 black soil, mixed with calcedonies, &c. ; and to the west of the road 



