118 SLATE DEPOSITS AND INDUSTRY OF UNITED STATES. 
east-west, like the quartzite farther south. Slate is also said to occur at points west 
of the road from the Springs to the church. The minimum width of this slate belt 
is half a mile. North of the church is a greenish metamorphic eruptive consisting 
of actinolite, zoisite, titanite, and sericitized plagioclase. South of the quartzite are 
greenish schists, possibly of similar origin. Between the church and Warrenton 
greenish schists also crop out at several points. They are epidotic actinolite schists 
in places with lenses up to 3 by 2 feet, and stratiform masses of an epidotic rock 
containing actinolite, titanite. magnetite, chlorite, and quartz. 
All these hornblendic and epidotic rocks weather into a bright reddish soil. This 
slate is thus related to a quartzitic formation, as well as to certain hornblendic and 
epidotic rock-, which must be regarded as metamorphosed eruptives." The prox- 
imity of the slate to these other formations is so close that nothing can be assumed 
as to it- thickness. 
slate has been prospected at three points, indicated by black dots on the map, 
fig. 1 l. < me is seven-eighth- of a mile north-northeast of the Springs, east of road to 
Warrenton and wesi of beginning of small brook flowing south into the Rappahan- 
nock. Cleavage strikes X. 80° E., dips 25° W. The plowed fields on the south 
show a strip of dark-gray soil, from the weathering of the slate, which measuro L25 
ieet across. The slate is black, and, to the unaided eye. has a coarsish texture, a 
rough, speckled cleavage surface with little luster. It is very carbonaceous; shows 
pyrite on sawn edges, and has about 220 cubes and lenses of pyrite to the square; 
inch, measuring one-fiftieth of an inch and under; no magnetite; nor effervesence 
with cold dilute hydrochloric acid. It has an argillaceous odor. 
Under the microscope this sho\n sn< (aggregate polarization, but a coarse cleavage, the 
matrix mainly of carbonaceous matter and quartz fragments with a little muscovite. 
The quart/, grain- measure from 0.009 to 0..'! mm.: quite a number of plagioclase 
feldspar fragments up to 0.2 mm. long. Lenses and cubes of pyrite coated with 
quartz, about 5 per square millimeter; a few scale- of chlorite: rare fragments of 
zircon. No carbonate or rutile detected. 
The chief constituents of this slate, arranged in descending order of abundance, 
appear to be: Carbonaceous matter, quartz, muscovite, feldspar, pyrite, and chlorite. 
This i- a clay-slate. 
At the locality about a half mile northeast of the Springs the cleavage strikes 
N. 25 1... dip- 20° W., bedding probably X. 12° W. Strike joint- strike X. 15° E., 
dip 90°; dip joints X. 7"> : W., dip 90°, but variable. The -late i- here covered with 
l' feet of black clay, and these by 3 feet of brownish yellow clay, both of which still 
show a lamination parallel to the cleavage of the underlying -late, and therefore 
represent different stages in the decomposition of the slate. 
Tins slate i- bluish black, to the unaided eye has a moderately line texture and 
cleavage surface with very few lenses of pyrite and but little luster. It is very car] 
bonaceous, show- pyrite on -awn edge, ha.- no magnetite, no effervescence in cold 
dilute hydrochloric acid, i- sonorous, and has an argillaceous odor. 
Under the microscope this ha- a matrix of muscovite I sericite I with distinct aggrej 
gate polarization but abundant irregular quartz grains from 0.009 to 0.37 nun.; also 
some lenses of secondary quartz, much carbonaceous matter, a few lenses of pyrite 
up to 0.14 nmi.. passing into limonite, a few grains of plagioclase feldspar. Xo 
carbi »nate or rutile detected. 
The chief constituents of this slate, arranged in descending order of abundance, 
appear to be muscovite "sericite), quartz, carbonaceous matter, pyrite. Recent 
excavations are said to show a larger amount of pyrite at a depth of 20 feet than 
the specimen above described indicates. This is a mica slate. 
The third locality is about a half mile south of the Springs, on the east bank of the 
Kappahannock. About 40 feet of "slate" are exposed in a small cliff. The strike of 
a Rogers, op. fit., refer.- to the epidotic ones 
