PENNSYLVANIA. 79 
and 390 feet in depth. In 1904 it was operated by two companies, Wm. Lobb & 
Sons at the western end and Stephen Jackson & Co. at the eastern end. The 
structure is an S-shaped fold overturned to the north-northwest. The bedding 
strikes N. 58°-60° E'.j cleavage at the north-northwestern edge dips 10° S., halfway 
down about 10° N., and at the bottom about 40° S. The grain is at right angles to the 
ribbon. At the north-northwestern edge of the quarry is a series of hard beds 40 
feet thick. Under the microscope this rock shows no aggregate polarization and con- 
sists of the following minerals, named in order of diminishing abundance: Carbonate, 
quartz, chlorite, carbonaceous matter, muscovite, pyrite, and rarely plagioclase feld- 
spar. It is a clay slate. Some of the beds are said to measure 20 feet between 
ribbons. There is an exceptional bed, 44 inches thick, of a dark, slightly greenish 
gray slate of superior quality, described beyond. Vein matter on the dumps consists 
of vein quartz and calcite, the former predominating. Associated with these veins 
are plicated very quartzose ribbons traversed by a coarse slip cleavage and also 
brecciated. Black slaty material has been pressed into the faults of the slip cleavage. 
One of these quartz masses was 20 feet thick and extended the entire length of the 
quarry. 
The chief product of the Albion quarry is a very dark-gray slate which, to the unaided 
eye, has a fine texture and a roughish almost lusterless cleavage surface. It is some- 
what carbonaceous or graphitic and magnetitic, shows pyrite on the sawn edge, effer- 
vesces slightly with cold dilute hydrochloric acid, considerably in the ribbon, and 
is sonorous. 
Under the microscope this slate shows a matrix of muscovite (sericite) , with brilliant 
aggregate polarization, somewhat obscured by abundant carbonate in plates and 
rhombs. The amount of carbonate is less than in the specimens from the Old Bangor 
and North Bangor quarries. Quartz is not very abundant, in grains measuring up to 
0.04, rarely 0.09 mm. Scales of chlorite, interleaved with muscovite, are conspicuous, 
lying transverse to the cleavage, sometimes forming lenses with their long axes par- 
allel to the cleavage, measuring up to 0.14 by 0.07 mm. and numbering about 20 per 
\ square millimeter. Pyrite spherules occur up to 0.01 mm. and average about 150 
'; per square millimeter. There is finely disseminated carbonaceous (or graphitic) 
I matter and a great abundance of rutile needles. 
The mineral constituents, arranged in descending order of abundance, appear to be 
muscovite (sericite), carbonate, quartz, chlorite, pyrite, rutile, carbonaceous matter, 
magnetite. The carbonate, although second, is not as abundant as in specimen from 
"Old Bangor" quarry. 
The results of Professor Merriman's physical and chemical tests of the dark-gray 
("black") slate from this quarry are here given for convenience of reference: 
Strength (modulus of rupture), 7,150 pounds per square inch; toughness (ultimate 
deflection on supports 22 inches apart), 0.270 inches; density (specific gravity), 
2.775; softness (amount in grains abraded by 50 turns of a small grindstone), 80; poros- 
ity (per cent of water absorbed in 24 hours), 0.238; corrodibility (per cent of weight 
lost in 63 hours in acid solution), 0.547; per cent of lime, 4.09; computed carbonate 
of lime, 7.40 per cent; computed carbonate of magnesia, 4.41 per cent.« 
The dark greenish-gray slate of the Albion quarry has to the unaided eye a some- 
what granular texture and a roughish and almost lusterless cleavage surface. It is 
not perceptibly carbonaceous or graphitic, but is somewhat magnetitic. The sawn 
^dges show pyrite. It effervesces slightly with cold dilute hydrochloric acid, and 
s sonorous. 
Under the microscope it shows a matrix of muscovite (sericite), with brilliant 
iggregate polarization. Quartz fragments measure up to 0.09 mm. There is consid- 
erable carbonate. There are chlorite scales, interleaved with muscovite, lying trans- 
aMerriman, op. cit. 
