76 SLATE DEPOSITS AND INDUSTRY OF UNITED STATES. 
of the Hudson formation, consists of small beds of harder slate separated by small ril 
bons which are not coarse enough to interfere with their use either as mill stock < 
roofing slate. 
The Bangor, East Bangor, Pen Argyl, Danielsville, Slatington, and Slatedale qua 
ries are in the "soft vein" beltand the Belfast and Chapman are in the "hard vein. 
Judging from the map of the Second Geological Survey, Pennsylvania, which repr 
sents a limestone area, presumably anticlinal in structure, as extending from tl 
Delaware near Portland to the vicinity of East Bangor, the "hard vein" ought i 
recur there near the limestone. 
The literature of the slate of Northampton and Lehigh counties will be found i 
the Bibliography on pages 138-145, under the names Chance, Lesley, Merrill, Men 
man, Rogers (H. D.), Sanders. 
A few typical- quarries and slates from these belts will now be described. 
NORTHAMPTON COUNTY. 
Bangor. — The "Old Bangor" quarry at Bangor, now operated by J. S. Moyer & Cc 
is the largest slate quarry in the United States and the oldest one in this region. It 
regarded as being near the top of the "soft vein" belt. It measures over 1,0( 
feet along the strike, 500 across it, and from 200 to 300 feet in depth. (See PI 
XIII-XV.) The general structure is a close overturned syncline, striking aboi 
N. 25° E., with an axial plane dipping east-southeast at a low angle and pitehii 
5°-10° SSW., crossed by cleavage dipping from 5° to 10° S. 32° E. There is a gritl 
bed both at the top and bottom of the quarry, which is regarded as the limit of tli 
slate — i. e., the lower limit, drill cores from a depth of 200 feet below the quan 
having failed to show any good slate. The thickest bed of good slate is S) feet thic 
Vertical diagonal joints striking N. 52°-57° E. are conspicuous. There are all 
vertical dip joints and horizontal ones. Curvature of the cleavage occurs here are 
there. Certain diagonal or longitudinal joints intersecting the bedding planes at t\ 
northern corner of the quarry produce an optical illusion, for the beds there seem i 
curve over to the west-northwest instead of the east-southeast, and thus, in co: 
nection with the syncline on the east-southeast wall, to form a complete ellipsoi 
The ribbons are markedly more calcareous than the slate, and in weathering becon 
white from incrustation of lime. Veins of white calcite and quartz, 4 inches thic 
occur in the strike joints. Crystalline films of gypsum were collected on the hoi 
zontal joint faces. 
The slate from the "Old Bangor" quarry is very dark gray, and to the unaidt 
eye has a fine texture and a fine cleavage surface, almost without any luster. Tl 
sawn edge shows pyrite. It contains very little magnetite, is carbonaceous or grap 
itic; effervesces with cold dilute hydrochloric acid, is sonorous, and has an argill 
ceous odor. 
Under the microscope this slate show T s a matrix of muscovite (sericite), with 
brilliant aggregate polarization, somew T hat obscured by abundant carbonate in plat 
and rhombs. The cleavage is regular, but the particles are coarse. There are occ 
sional chlorite scales up to 0.124 by 0.066 mm.; quartz grains not very abundant i 
to 0.047 mm. Pyrite spherules number about two hundred per square millimett 
measuring up to 1.01 mm. in diameter. Rutile needles are very plentiful. Carb 
naceous or graphitic matter occurs in fine particles throughout. 
A tranverse section of a coarse ribbon from this quarry showed, under the micr 
scope, bedding crossed by cleavage at an angle of 27°, a matrix of sericite in irregul 
stringers, without any aggregate polarization, and carbonate and carbonaceous mi 
ter, containing angular quartz grains up to 0.17 by 0.12 mm., feldspar grains (plagi 
clase, orthoclase) up to 0.14 by 0.09 mm., the quartz and feldspar together makii 
up no more than 25 per cent of the ribbon; also spherules of pyrite up to 0.07 nm 
