44 
BALL AND SIMPSON: COALFIELDS OF INDIA. 
has been traced for 20 miles. An enormous amount of coal has been 
rendered worthless by these igneous intrusions. 
Coal-seams are found in both the Barakar and Raniganj sub- 
divisions of the Damuda series ; these groups being separated from 
one another by the Ironstone Shales. According to Blanford, in the 
Barakar beds, four seams with an aggregate thickness of 69 feet 
have been worked, and in the Raniganj stage, 10 seams with an 
aggregate thickness of 110 feet, whilst many other seams are known 
to occur within the field. Presuming that an average thickness of 
50 feet of workable coal occurs throughout the area of 400 square 
miles occupied by the coal-bearing rocks, and that the average 
specific gravity of the fuel is 1 -393,1 ^j^g ^^^^^i quantity of coal 
within the field would be 21,671 million tons. Closer estimates of 
the quantity of coal from the best seams now in sight are given below. 
By far the greater portion of the output of coal is drawn from 
the Raniganj or Upper measures and the major portion of this 
from two seams — the Dishargarh and Sibpur seams. Other seams 
of importance are the Sanctoria, Ghusic and Raniganj seams. 
In the Barakar or Lower measures no one seam can be traced 
for any considerable distance, but thick seams are worked at about 
the same horizon at Laikdih, Ramnagar and Salanpur. Good coal 
is also worked at Begunia near Barakar, at BorreS, and at 
Gaurangdi. 
A fault with a throw of several hundreds of feet traverses the 
coalfield from north to south and divides it roughly into two halves. 
Parallel with this fault, but about a mile to the west, the great 
basaltic intrusion known as the Salma dyke can be traced right 
across the field and into the crystalline rocks in both directions. 
These structural features appear to have profoundly affected the 
coal seams, and correlation between the seams on either side of 
the break is difiicult. Another pronounced fault with a parallel 
direction and even greater throw can be traced between Ikrah and 
Raniganj. Correlation of the seams on either side of this fault is again 
very uncertain. There is a marked deterioration in the quality of 
the coal passing from west to east, and it is a fair general- 
ization to say that there is no first class coal worked east of this 
fault. 
1 Bee, G. 8. I., X, 15U (1877). 
