The Banaganapilly sandstone of the Kurnool formation is 10 to 20 feet thick, and is the only rock of that region in which the diamond is known to be found. Dioings are carried on in many parts of the country on or near the Kurnool formation, but mostly in the superficial gravels. At Banaganapilly, however, there have been extensive workings in the bottom sandstone. Shallow pits, not more than 15 feet deep, are sunk in the sandstone, and short galleries driven in the diamond layer, which must be at the very base of the group, or close to the bottom bed. In this locality the workings of the diamond miners are crowded over particular spots, whilst large areas adjoining, of the very same deposits, are left untouched. If this irregular working be only due to some delusion of the diamond seekers, a large field still awaits exploration. The Cud dapah geological formation has four great groups, called the Krishna, Nullamallay, Cheyair, and Pampugui groups. These consist of slates and quartzites. The Cuddapah basin is about 210 miles long, and of a crescent shape. Its N.E. horn is the Palnad, and reaches to Juggiapet, a few miles N. of the Krishna river, an area of 13,500 square miles. Afore than a third of the area is taken up by the overlying Kurnool formation.
The Banaganapilly district is about 30 miles long from N. to S., and 26 in breadth from E. to 1V., lying between lat. 15° and 16° N. in the centre of the Ceded Districts. its E. and S. part consists of a fertile plain of the regur or cotton soil, bounded on its N. and S. aspects by detached ridges of bills of clayslato and sandstone, which run from Kurnool towards Ghooty, Cuddapah, and Tripati, and termhuito at Naggeri, NAV. of Afadras. The 13anaganapilly diamond mines are situated in and near a low range of hills about half a mite from the town. The diamond mines near Cuddapah are about 7 miles N.E. from the town, on both banks of tho Pennar river, where this washes the foot of a range of hills. The mines at Cuddapah have, it is said, been worked for several hundred years with various success. In the Chinnur taluk, in which Cuddapah is the largest town, there aro two places, called Conda petta and Ovalumpilly, where diamonds occur. In the next taluk, on the west side of this, diamonds are dug at Lamdur mid Panchatgapadu. Several mines extst near Ghooty.
The Ovalumpilly mines are on the west side of the river, about 6 miles from Cuddapab, and 3 miles from the Kanaperty mines. They are situated on a gentle ascent, about half a mile from the Fennar, in a well-cultivated country, and within a very short distance of three villages. They aro chiefly on ground belonging to Ovalum pilly.
In the mines at Cuddapah, the uppermost stratum consists of sand or gravel, mixed with a small proportion of loam. Its thickness scarcely
exceeds a foot and a half. Immediately under it is a bed of stiff bluish or bLack mud, similzu. to what is seen in places that have been inundated. It is about 4 feet thick, and contains no stones. The diainond bed comes next, and is easily distinguished from the incumbent bed, by the great number of large rounded stones which it contains. It is about 2 or 2f feet thick, and is composed of large round stones, pebbles, and gravel, c,emented together by clay ; in the dry seasons, it is as dry as the bed which lies immedi ately above.
At Ranzalcoltah, about 20 miles from Kurnool, are many diamond pits in small ferruginous gravel. Iron ore, red hematite, occurs in all the hills in the neighbourhood of Ramalcottah. There are also diamond mines at Munimadagu, and 1Vudjar Karur near Ghooty; and during the Mahomedan rule diamonds were dug in the Sidhout Hills, a continuation of the Nullamallay range, and also near the village of Durjipilly. Diamond mines occur at Naikenabad MulLanarum, near Timmericottah, and in the bed of the Kistna river near Nagajurecondah.
Sandstone conglomerate extends eastwards from Banaganapilly to Condapilly and Afallavelly, in all which localities diamonds aro found.
Mallavelly, a village 16 miles 1V.S.IV. of Ellore, is ono of seven villages near which diamond mines exist. The names of the other six villages in which diamonds aro found are Gani Partala or Partial, Atkur, Burthenypada, Pertalla, Wustapilly, and Kodavetty Kallu. At Sfallavelly, tho hollow flat where the diamond pits aro excavated is a low swampy plain. Being surrounded by a bank or rising of the soil in a circular manner, it has the appearance of having been once a lake. The banks are formed of the red ferruginous sandy soil prevailing all round this place. The diamond pits are in general excavated at the north end of the bank that surrounds the hollow. The deepest could not be more than 12 feet, and they never came to a hard mass of rock.
Partial is about 50 miles from Masulipatam, but the diamonds were of small size, .and the searchers did not earn 4 or 5 rupees a month. In the northern diamond mines, particularly those of Partial, Dr. He3rnes found in the diamond bed a great number of fine chalcedony and cornelian pebbles and garnets. The larger stones formed the greatest part of the diamond bed.
The district of the diamond mines of Golconda WM ceded to the Nizam by the British under a special treaty, but is enclosed by British territory. Diamond mines not far from Condapilly are con stantly worked. There aro none found at Gol conda, or in the Golconda district, but they were formerly out and polished there.