Kistna
and Godavari. Loose stones are occasionally picked up from the ground.
The stones have been obtained from the alluvium and from workings in
the Banganapalli stage of the Kurnool series of strata. No official
returns of production are available, but a number of small and at times
valuable diamonds have been reported as picked up after showers of rain
round Wajrakarur in the Anantapur district. Some years ago a stone
weighing 60 carats was found and was expected to sell at a lakh of
rupees.
During
1910-12, Mr. A. Ghose prospected the Virayapalle area in the Karnul
district. He found that the diamond bearing conglomerate was found to
vary in thickness from 3 in. to 2 ft. Sixteen cubic feet of the rock
were found to yield 1/6 to 1/2 a carat of diamond. The stones were
perfect crystals of fine quality and free from flaws. Since then there
is no information on output or mining in Madras.
Anantapur district.—
There is a volcanic neck, filled with a decomposed basic rock at
Wajrakarur (15° 2' : 77° 27') similar to the matrix of diamonds at.
Kimberley, but no stones have been obtained from the rocks of the pipe.
It is a highly altered plagioclase-augite rock, not similar to the blue
ground. A stone valued at £10,000 was once obtained from the
neighbourhood. In 1861 a diamond weighing 67-3/8 carats was cut by
Messrs. P. Orr & Sons, Madras, to 24-5/8 carats.
Diamonds
were regularly picked up year by year in the fields surrounding the
pipe to a distance of about 3-4 miles from it. It is impossible to
estimate the value of the finds but direct attention to the pipe itself
has so evidently proved unprofitable. Sir C. S. Fox, who visited the
area in 1930 is of the opinion that the diamonds of the fields near
Wajrakarur have weathered out of the pipe rock. According to him the
pipe rock though agglomeratic in constitution is more clearly allied to
the doleritic intrusions of the Lower Cuddapah than to the Kimberlites
of South Africa.
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