108 SLATE DEPOSITS AND INDUSTRY OF UNITED STATES. 
The following analyses were made by Dr. W. F. Hillebrand in the laboratory oj 
the United States Geological Survey: 
Analyses of Vermont "purple" and "variegated" roofing slates. 
Si0 2 (silica ) 
Ti« >., (titanium dioxide i 
Zr0 2 (zirconia) 
A1 2 3 (alumina) ! 16.33 
I '. 1 i . i ferric oxide i 
Fe() (ferrous oxide | 
MnO (manganous oxide 
NiO (nickelous oxide i . . 
CoO cobaltous oxide . . 
i !a< i i lime i 
BaO (baryta) 
Mg< ) i magnesia i 
t.10 
2.71 
.09 
Trace? 
Trace? 
.50 
.06 
2. 92 
H. 
K ,( i i 1 .. »tassa ) 5. 54 
>da) 
Li 2 (lithia) 
B 2 (water below L10°C.) 
E 2 watei above L10' C 
P 2 i > , phosphoric oxide) 
rbon dioxide i 
FeS 2 pyrite) 
-' ' , sulphuric oxide) 
C (carbon) 
Total.. 
s (total sulpb 
ir above) 
L.26 
Sir. Ir. 
,:;i 
3.24 
.16 
. 11 
.ni 
1 race. 
None. 
60. 96 
.86 
Trace.' 
16. L5 
5.16 
2:54 
.07 
Trace. 
Trace. 
.71 
.01 
3.06 
5. 01 
1 . 50 
Trace. 
. 17 
3.08 
. 23 
.68 
None. 
None. 
99.98 
.02 
100.22 
.07 
Specific gravity 2.8064 
IK 
CO. -J I 
.92 
Trace? 
is. it; 
•_>. 56 
5. L8 
.07 
Trace. 
Trace. 
.33 
.03 
2.33 
4.09 
1.57 
Sir. tr. 
. L8 
3.81 
.11 
.08 
.16 
None. 
100. 12 
.087 
2.8053 
G D XIV, '95, 260a), purple roofing slate, McCarty quarry, easl of center of Lake Saint Catherii 
South Poultney, Vermont. II I l». XV,'95,760a , purple roofing slate, Francis & Sons quarry, nea 
a mile south of Hydeville, in (Jastleton, Vermont. I ( l>. XV, '95, 31 1 1, variegated roofing slate, fr< 
Eureka quarry, 3i miles north of Poultney, in Poultney Township, Vermont, "unfading-green" ar 
II- i D. XIV, '95, 614a), dark reddish bed a few inches thick in purple of sea-green area, wesl 
Lake Saint Catherine; determination of iron oxides only. 
The results of certain tests of the strength of Fair I la von "purple" slate are giv 
on page ! 2 I. 
The purple and variegated slates are used mainly for roofing. 
Mill-stock slate. -In the northern and western pari of the green-slate belt th< 
beds which have a less perfect cleavage are used as mill stock, and find a market I 
blackboards, billiard-table tops, electric switchboards, tiles, vats, mantels, etc., an< 
for some purposes are subjected to the process known as ' ' marbleizing. " They an j 
purple or green. The purple is frequently paler than the purple roofing slate, an< 
also spotted with green, while the green is sometimes brighter than the unfadia 
green rooting slate. 
Specimens from the Scotch Hill quarries, 2 miles north-northeast of Fair Haven 
from the Meadow quarry, one-fourth mile east of Fair Haven; from the Lake Homo 
seen Slate Company's quarry at Cedar Point, on Lake Bomoseen,« and from th 
J. Jones quarry, 2\ miles north of Castleton, were examined microscopically, witl 
these resuRs: 
The matrix is muscovite (sericite), with aggregate polarization, but shows a clea"\ Li 
'See pi. XXIV, .v. for the structure at this quarry. 
