88 ECONOMIC GEOLOGY OF AMITY QUADRANGLE, PA. 
COAL. 
GENERAL STATEMENT. 
Coal is destined to become the most important mineral resource of 
the Amity quadrangle. Owing to the depth of the principal seam 
below the surface, only a few mines are in operation at the present 
time, but the demand for coal is increasing with its exhaustion near the 
surface, and in time shafts will be sunk over much of the quadrangle 
and operations conducted on a large scale. 
The principal coal beds outcropping in the quadrangle are the Pitts- 
burg, Redstone, Sewickley (Mapletown), Waynesburg, Waynesburg 
"A," and Washington. The Pittsburg bed is the only one mined for 
shipment, but the Waynesburg is worked at many country banks, and 
one bank is known on the Redstone and several on the Sewickley seam. 
The Waynesburg "A" is probably worthless and the Washington coal 
is generally too poor to be of value under existing conditions. Several 
seams below the Pittsburg have been penetrated by the drill in search 
of oil and gas. 
PITTSBURG COAL*. 
GENERAL STATEMENT. 
The Pittsburg coal is the most valuable bed in southwestern Penn- 
sylvania. From all the evidence obtainable it seems to be of workable 
thickness throughout the quadrangle and its quality is usually superior 
to that of the other coals of the region. The Pittsburg coal occurs at 
the base of the Monongahela formation, or Upper Productive Meas- 
ures. (See columnar section, PI. I, pocket.) Fig. 4 shows the total 
area] extent of the seam in Pennsylvania, together with the relative 
location of the Amity quadrangle. In this quadrangle the outcrop of 
the bed is only about L5 miles in length, but with the exception of the 
two small areas where it is cut by Chartiers and Peters creeks it is 
believed to underlie the entire district, a total area of 228 square miles. 
The 4 average workable thickness of the bed being estimated at 6 feet 
and the specific gravity of Pittsburg coal in this region as 1.29, a the 
quadrangle contains 37,260,710,400 cubic feet,or 1,500,632,315 short 
tons (about 1 ,300,000,000 long tons). The coal has been estimated to 
underlie 833 square miles out of the total area of 858 square miles in 
Washington County. 
The extent of the Pittsburg coal outcrop is shown on the geologic map 
(PL I, pocket) by the blue line at the contact of the* Conemaugh and 
Monongahela formations. The outcrop of the coal follows both sides 
of Peters Creek below Venetia and of Chartiers Creek below McGovern, 
and the bed also reaches the surface at Meadowlands, where it out- 
«The figure 1.29 is p.n average of the specific gravity of coal from three mines in the region, deter- 
mined by the fuel-testing plant of the United States Geological Survey at St. Louis, Mo. 
