WEST VIRGINIA. 121 
The only quarry yet opened is that of the Shenandoah Slate Company, about 3 
miles northeast of Martinsburg, near a small run flowing into the Opequon. When 
visited in May, 1904, the quarry measured about 100 feet along the strike, 70 feet 
across it, and 75 feet in depth, of which the "top" took up 25 feet. The bedding 
strikes N. 25° E., dips about 15° E. The cleavage, with the same strike, dips 75° E. 
There are joints striking with the cleavage and dipping 35° E., dip joints striking \. 
50° W., dipping 90°. The beds are small and are separated by darker ribbons. The 
thickest bed exposed measured 3 feet 6 inches. A diamond drill core from down to 
40 feet below the bottom of the quarry shows several 3-foot beds. 
The slate is black, with a slightly brownish hue. The texture is somewhat fine 
and the cleavage surface roughish without any luster whatever. The material is 
carbonaceous rather than graphitic, contains a little magnetite, shows pyrite on the 
sawn edge, effervesces with cold dilute hydrochloric acid, but less in the ribbon, is 
somewhat sonorous, and has an argillaceous odor. Under the microscope it shows a 
matrix consisting of carbonate and carbonaceous matter, and therefore' without 
aggregate polarization, but a cleavage consisting in the parallel arrangement of the 
carbonate and carbonaceous matter in alternating bands. A very carbonaceous bed 
(ribbon) crosses the cleavage at an angle of 36°. There are abundant angular quartz 
grains up to 0.05 millimeter; scales of chlorite interleaved with muscovite, and some 
of muscovite only; spherules of pyrite up to 0.01 millimeter, numbering about 240 
per square millimeter. Rutile not observed. The amount of carbonate differs in dif- 
ferent beds. It may be so abundant as to obscure completely the sericitic matrix. 
Some of the sections parallel to the cleavage show almost as much muscovite as carl ion- 
ate and, curiously, a faint aggregate polarization parallel to the bedding or the grain. 
The constituents of the Shenandoah Slate Company's slate, arranged in descending 
order of abundance, appear to be carbonate, muscovite (in places almost equal in 
amount to carbonate) , quartz, kaolin, pyrite, carbonaceous matter, chlorite, magnetite. 
This is a clay-slate. The amount of C0 2 (carbon dioxide) in this slate was determined 
by Mr. George Steiger, chemist of the United States Geological Survey, at 1 .94 per cent. 
An analysis of slate from this quarry, made for the company by Dr. W. C. Tilden, 
of Washington, shows Si0 2 , 62.71; A1 2 3 , 19.40, and CaO, 1.11 per cent. It is pro- 
posed to use the product of this quarry for mill stock, for which it seems better 
adapted than for roofing. 
The following prospects were noted: One 2 miles south of Martinsburg, on John 
Rowe'sland, where an opening 30 by 20 feet hasbeenmade. Bedding strikes N. 32° E., 
dips 60°-65° E.; cleavage strikes X. 23° E., dips 80° E. A 3-foot bed is in sight. 
Another opening has been made on the Opequon, on Light's land, a half mile south- 
southeast of Bedington (a little north of the north limit of map). Bedding and 
cleavage strike N. 20° E., the former dipping 30° E., the latter 55° E. A 3-foot bed 
is in sight. Under the microscope this shows a faint aggregate polarization, frag- 
ments of feldspar, and rutile needles. At an opening on T. F. Bowers's farm, about 4 
miles northeast of Martinsburg, the cleavage strikes N. 27° E. and dips 73° \\\, but 
bedding dips east. Under the microscope this also shows a faint aggregate polar- 
ization, but carbonate is unusually abundant and evidently obscures the cleavage. 
In the brook on John Shedd's farm, 2£ miles south-southeast of Martinsburg, the 
cleavage strikes N. 20° E. Under the microscope this shows a slight aggregate p< >lar- 
ization and but little carbonate. Clay-slate has also been found on the McKown and 
Busey farm, 2 miles N. 10° W. from Middleway, in brook 2\ miles southeast of 
Martinsburg, and also on land of J. W. Snyder on the Opequon, 3 miles southeast of 
Martinsburg, and it will be found in many other places. 
Although the proportions of carbonate and muscovite vary in these slates, none of 
them show a complete sericitization of the matrix. They are all clay-slates. The 
material can therefore hardly possess sufficient fissility or prove sufficiently strong or 
elastic to compete with mica-slates for roofing purposes. Furthermore, the amount 
of carbonate shown by the microscope, as well as the mode of weathering by the 
