My Guess
According to the Internet unbroken bituminous coal has a weight of 84lbs per
cubic foot.
This is more or less one ton per cubic yard
Therefore we are looking at 2,280,000 cubic yards.
At 4ft 6ins thick we are looking at 1,520,000 square yards of solid coal.
One acre is 4840 square yards.
Therefore a solid area of coal weighing 2,280,000 tons at 4ft 6ins thick,
would occupy 314 acres.
You would now have to factor in what the extraction rate is? I suspect that
30% would be something like. This would give around 1050 acres. There are
640 acres in a square mile - giving an area of 1.64 square miles.
At the end of the day it all depends on extraction rates - losses due to
faulting, bad coal, pillars etc.
Hope this helps.
Dave.
-----Original Message-----
From: mining-history [mailto:[log in to unmask]] On Behalf Of M J
Shaw
Sent: 18 December 2011 18:28
To: [log in to unmask]
Subject: coal
The Hanwood coalfield around Shrewsbury had three seams of coal, the Yard,
Half Yard and Thin whose total thickness rarely achieved 6 foot. Is anyone
willing to hazard a guess as to how many acres (square miles?) would need to
be mined in the late 19th century, assuming uniform seam thickness, to
extract 2,280,000 tons from just the first two of these seams, four feet six
inches max in total, over 21 years.
Michael Shaw
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