16 SLATE DEPOSITS AND INDUSTRY OF UNITED STATES. 
rounded by an aggregation of spherules of pyrite in a cloud of rutile needles. There 
are also cracks filled with secondary sericite. In the surrounding purple the same 
elements recur, but the pyrite is much more abundant, measuring up to 0.021 mm. 
There are also many dots of Fe 2 3 from less than 0.003 to 0.009 mm., and rutile needles 
up to 0.012 mm. in length. 
An elliptical green spot, 3 inches long, with a purple rim, in Ordovician red slate 
from the National Red Slate Company's quarry north-northwest of Raceville (Speci- 
men D. XIV, '95, 397a), when cut transversely to the cleavage, measures a half inch 
in thickness and shows a black streak 1 inch long in the center. The central streak 
consists of strings of minute irregular lenses of cryptocrystalline quartz and possibly 
carbonate of manganese (rhodochrosite) containing spherules of pyrite. The green 
part consists of a mass of fibers of muscovite, which polarize as one mineral with 
much carbonate and many lenses, and also quartz grains. In the purple rim there 
is a decrease of carbonate and the hematite fragments begin to appear and become 
still more abundant in the surrounding red slate itself. 
A green spot in Ordovician red slate (D. XIV, '95, 201c), from the Empire Red 
Slate Company's quarry, a mile north of Granville, cut parallel to the cleavage, shows 
slate needles (Ti0 2 ) up to 0.043 mm. long, carbonate rhombs up to 0.030 mm., chlo- 
rite scales up to 0.030 mm., angular quartz grains up to 0.039 mm., and prisms of 
tourmaline up to 0.021 by 0.002 nun. The surrounding red slate, that of Analysis 
K, p. 73, has been described in the general description on p. 72. 
Another spot, almost circular, 0.44 inch in diameter, from a piece of red slate (D. 
XIV, '95, 201 1) from the same quarry, cut parallel to the cleavage, shows a central 
dot 0.03 inch in diameter, consisting mainly of carbonate and of a dense brown mate- 
rial. About this is a zone about 0.1 inch wide, of elliptical shape, of carbonate, with 
some fibrous quartz along the margin. Then comes a zone 0.08 inch wide, of green 
slaty material, containing angular quartz grains, muscovite scales, rutile needles, 
nodules of pyrite, and thinly disseminated areas and rhombs of carbonate; then a 
very narrow zone, made up entirely of carbonate and pyrite. Outside of this, another 
green slate zone, 0.08 inch wide, like the first, but with very little carbonate. The 
angular quartz grains measure up to 0.030 mm. There are also slender tourmaline 
prisms. Outside of all comes the red slate, full of Fe 2 3 pigment. Chlorite was 
not detected in the green zones, but it may be present in minute scales. 
CHEMICAL ANALYSES OF SPOTS IN RED SLATE. 
The specimen (Q, R) analyzed by Doctor Hillebrand came from the same quarry 
as the large spot described above. It was a green spot with purple rim, in red slate. 
The analysis of the red slate M, on page 73, is repeated for comparison. 
Chemical analyses of spotted red slate. 
Si0 2 (silica) 
Ti0 2 (titanium dioxide, 
rutile) 
A1 2 3 (alumina) 
Fe 2 3 ( ferric oxide) 
FeO (ferrous oxide) 
MnO (manganous oxide) . 
NiO (nickelous oxide)... 
CoO (cobaltous oxide) . . . 
CaO (lime) 
BaO (baryta) 
Specimen 
a 
M. 
Q. 
R. 
63.88 
64.59 
65.44 
.47 
.51 
.52 
9.77 
10.23 
9.38 
3.86 
1.79 
1.09 
1.44 
1.19 
1.06 
.21 
.26 
.32 
Trace. 
Trace. 
Trace. 
Trace. 
Trace. 
Trace. 
3.53 
4.07 
4.53 
.05 
.05 
.06 
MgO (magnesia) 
K 2 (potassa) 
Na 2 0(soda) 
Li 2 (lithia) 
H 2 (water below 110° C. ) 
H 2 (water above 110° C.) 
P 2 5 (phosphoric oxide). 
C0 2 (carbon dioxide) 
FeS 2 (pyrite) 
Total 
Specimen. « 
«M ( = D. XIV, '95, 397 a), red slate, 1 mile north-northwest of Raceville, in Granville, Washington 
County, N. Y., about a spot; Q, purple rim of the spot; R, green portion of the spot. 
