VIRGINIA WEST VIRGINIA. 1 1 ( .t 
cleavage and bedding (?) ranges from \\ 80° E.to X. 85° W., dipping south al angles 
varying from 12° to 15°. 
The slate is bluish black, has a coarse crystalline texture, and, as accurately 
described by Rogers/' a knotty, wrinkly surface. This is due to the presence of 
cubical and lenticular cavities once occupied by pyrite bul now partially filled with 
quartz and graphite. These measure from one tc three-fiftieths of an inch and num- 
ber from 12 to 20 per square inch. The surface has very little luster. The slate is 
carbonaceous or graphitic, shows pyrite on the sawn edge, has very little magnetite, 
in places scales of a micaceous mineral up to one twenty-fifth of an inch, does riol 
effervesce in cold dilute hydrochloric acid, has an argillaceous odor, and is very 
sonorous. 
Under the microscope it shows a matrix of carbonaceous or graphitic material, 
quartz, and muscovite. As the first two predominate the aggregate polarization is quite 
faint, The cleavage is serpentine, owing to the many large quartz grains (up to 0.14 
millimeter) and the cubes ami Lenses or distorted cubes of pyrite already referred 1m. 
most of which seem to be partial pseudomorphs of quartz and graphite after pyrite, 
the remaining pyrite having been oxidized and dissolved. Therearesome plagioclase 
feldspar grains almost as large as the quartz grains, with graphite inclusions parallel 
to the multiple twinning. There are veinlets of quartz and lenses of secondary 
quartz usually about or on either side of the cubes and lenses of pyrite; rare grains 
of zircon. No carbonate or rutile detected. 
The chief constituents of this, arranged in descending order of abundance, appear 
to be carbonaceous matter and graphite, quartz, muscovite, kaolin, pyrite, and feldspar. 
It seems to be more metamorphic than that of the other localities, yet less micaceous. 
This is properly a graphite-quartz-muscovite-schist, or in process of becoming such. 
A piece of this "slate" a half inch thick from the roof of one of the brick outbuild- 
ings at the White Sulphur Springs, where it was ])laced at least sixty-eight years 
ago, does not show any decomposition, but in places has a little limonite coating. 
The pyritiferous character of all these Fauquier County shoe prospects and the 
sulphurous character of the springs are probably intimately related. Such springs 
are common in the vicinity of pyritiferous shale and obtain their sulphur from the 
decomposition of the pyrite by surface water. The indications from the openings 
and the microscopic examinations are not sufficiently promising to warrant invest- 
ments. 
The principal features of Virginia slate, as given in the foregoing descriptions, will 
be found in tabular form opposite page 124. 
WEST VIRGINIA. 
By T. Nelson Dale. 
This recently prospected slate district lies near Martinsburg, in Berkeley County, 
within the geological belt designated in the Harpers Ferry folio of the I Fnited State- 
Geological Survey as "Martinsburg shale." Brief preliminary notices of it have 
appeared in Bulletin No. 213 (p. 363) and again in Bulletin No. 260 (p. 538). This 
belt lies about 13 miles west of the Blue Ridge and mostly on the western side of 
Opequon Creek, a small tributary of the Potomac. It measures at least 14 miles in 
length from north-northeast to south-southwest and from 2 to 3 miles in width. 
The accompanying map (rig. 15) shows the geological relations and the principal 
outcrops. This shale and clay-slate formation, estimated at from 700 to 1,000 feet in 
thickness, is of Ordovician age and overlies the Cambro-Ordovician "Shenand »ah 
limestone" in a series of folds represented in the folio as overturned to the west. 
The rock is generally a dark-grayish shale, weathering into a yellowish or white 
clay, known locally as "soapstone." At several points, usually near the Opequon 
a Op. cit., p. 460. 
