VERMONT. 1()7 
The following analyses were made in the laboratory of the United States Geological 
Survey by Dr. W. F. Hillebrand: 
Analyses of Vermont "unfading green " roofing slates. 
SiOo (silica) 
Ti0 2 (titanium dioxide, rutile) 
ZrOo (zirconia) 
AL0 3 (alumina) 
Fe 2 3 (ferric oxide) 
FeO (ferrous oxide) 
MnO (manganous oxide) 
NiO (nickelous oxide) 
CoO (cobaltous oxide) 
SrO (strontia) 
CaO(lime) 
BaO (baryta) 
MgO (magnesia) 
KoO ( potassa ) 
Na 2 (soda) 
59.27 
.99 
is., si 
1.12 
6.58 
.13 
Trace? 
Trace? 
.42 
.05 
2.21 
3.75 
1.88 
59. is 
L.02 
Trace? 
18. 22 
1.24 
6. 81 
.07 
Trace. 
Trace? 
.56 
. 05 
2.50 
3.81 
1.55 
Li.,0 (lithia) 
IbO (water below 110° C.) .. 
H 2 (water above 110° C.) .. 
P.O.-, (phosphoric oxide 1 
C0 2 (carbon dioxide) 
FeS 2 (pyrite) 
S0 3 (sulphuric oxide 1 
C (carbon) 
Fl (fluorine) 
Total . 
S (total sulphur included 
above ) 
Specific gravity 
0. 32 
3. 98 
.11 
.21 
. 15 
Trace. 
None. 
99. 98 
.08 
2. 795 
Trace. 
0. 17 
4.05 
. 10 
. 39 
.13 
None. 
.(IS 
100. 23 
E ( = D.XIV, '95. 314/), Eureka quarries, 3£ miles north of Poultnev, in Poultney Township Ver- 
mont, F ( = D.XV, '96, 645a), Valley Slate Company quarry, 2h miles north of Poultnev in Poultnev 
Township, Vermont. 
The results of Professor Merriman's recent tests of Vermont unfading green slate 
will be found on page 123. 
This slate is largely used for roofing purposes. The mill stock slate is described 
beyond. 
"Purple" and "variegated" slate. — The "purple" plate is dark purplish brown; 
the "variegated" is like the "sea green" and the "unfading green," but is irregu- 
larly patched with purplish brown. These purplish slates are interbedded both with 
the sea green and the unfading green, as shown in the quarry diagrams (Pis. XXIII, 
XXIV). The texture, surface, and luster correspond generally to those of the slates 
I with which they are interbedded. The purple of the sea-green areas discolors less 
than the sea green, but effervesces with cold dilute hydrochloric acid, and is very 
slightly magnetitic. The variegated of the Eureka quarry does not effervesce with 
cold dilute hydrochloric acid. All these slates are sonorous. 
Under the microscope the purplish slate closely resembles the green, with which 
it is associated, both in structure and composition, excepting that the purplish con- 
tains a large amount of hematite (Fe 2 3 ) in irregular bright red dots from 0.001 to 
0.003 mm. in diameter, exceptionally in hexagonal scales. This mineral obscures 
the aggregate polarization. There are quartz fragments up to 0.047 and even 0.07 
mm., rare plagioclase grains; lenses of quartz a millimeter long, muscovite and 
chlorite scales lying at an angle to the cleavage, others without arrangement. 
Carbonate is less abundant than in the respective green slates. Spherules of pyrite 
[from 0.007 to 0.027 mm., rutile needles in abundance, a few prisms of tourmaline 
land rare fragments of zircon. 
The chief constituents of the "purple" slate, arranged in descending order of 
abundance, appear to be muscovite (sericite), quartz, chlorite, hematite, carbonate, 
jrutile, pyrite, magnetite. The purplish color is due to the mixture of the red from 
[the hematite and the bluish green from the chlorite. a In the variegated slates the 
mottling is produced by the irregular distribution of the hematite. 
I 1 « For colored lithographs of magnified thin sections of the "purple" slate, as seen under both ordi- 
nary and polarized light, see Nineteenth Ann. Rept. U. S. Geol. Survey, pt. 3, PI. XXXVII. 
