106 SLATE DEPOSITS AND INDUSTRY OF UNITED STATES. 
Analyses of Vermont "sea-green" roofing slate — Continued. 
HoO (water above 110° C.) 
ivi >, i phosphoric oxide) .. 
C0 2 (carbon dioxide) 
FeS 2 (pyrite) 
S< >. (sulphuric oxide) 
C (carbon) 
A. 
2.98 
.07 
. 10 
.22 
Trace. 
None. 
Fl (fluorine) 
Total 
S (total sulphur above) 
100. 07 
.12 
B. 
3.71 
.06 
.87 
.or. 
Trace. 
Strong 
trace. 
99. 80 
.032 
C. 
3: 41 
.09 
.05 
Trace. 
Trace. 
.11 
100.28 
.024 
A (=D. XIV. 1895, 230a), Rising & Nelsons quarry No. 2, West Pawlet, Vermont; 13-foot bed. 
B (=D. XIV. 1895, 225/ . Griffith & Nathaniel's quarry, 9 miles north of A, South Poultnev, Vermont. 
C (--I). XIV. ls'.i."). 2.")i - .' i. Wm. II. Hughes's quarry No. 10 (Brownell), 2 miles north of A, Pawlet,. 
Vermont. D i =1). XIV. 1895, 35/) . Auld & Conger's quarry, 8 miles north of A, in Wells, Vermont;] 
22 fool bed. Determination of silica only. These are all from the West Pawlet and South Poultney-' 
belt. 
Specific gravity: C, 2.7910; D, 2.7627. 
This slate i> used exclusively for roofing purposes. The results of Professor Mea 
riman's recent tests of it are stated on page 123. 
"Unfading green" slate. — This slate is greenish gray in color, and to the unaided 
eye has a somewhat line texture and a roughish lusterless cleavage surface. The 
sawn edge shows some pyrite. It is magnetitic, does not effervesce with cold dilute 
hydrochloric acid, and is sonorous. Several years' exposure produces so little change 
of color thai only when a fresh slate is put beside it is any change perceptible, and 
that is bul slight. Its lissility is interior to thai of the "sea green." Under the 
microscope it shows a matrix of muscovite (sericite), with a brilliant aggregate 
polarization but considerable inequality in texture, coarser quartzose bands, witl 
imperfect cleavage, alternating with liner more sericitic ones. In both there I 
irregularity in the size of the particles. Angular quartz grains measure from 0.01 by 
0.008 to 0.04 by 0.017, rarely 0.07 by 0.017 mm. There are a few lenses up to 0.2 by 
0.1 nun. of quartz fragments and muscovite scales, also lenses up to 0.4 by 0.1 mm. 
of chalcedonic quartz?. A few grains of plagioclase feldspar, scales of chlorite tip to 
0.039 by 0.006 mm. parallel to the grain and also scales of muscovite in similar posi- 
tion. Not a few specks and Lenses of pyrite, some octahedra of pyrite with rim of 
chlorite, carbonate rhombs — 0.026 to 0.065 mm.— but in very much smaller number 
than in the sea-green slate. Abundant rutile needles from 0.003 to 0.008 mm. long, 
The chief constituents of this slate, arranged in descending order of abundance. 
appear to be muscovite ( sericite i, quartz, chlorite, carbonate, rutile, pyrite, magnetite* 
These slates are relatively unfading, because they have fewer rhombs and plates 
of carbonate.'' The sections also show why they cleave less perfectly than the 
sea-green slates. 
a For colored lithographs of magnified thin sections of this slate, as seen both under ordini 
polarized light, see Nineteenth Ana. kept., pt. 3, PI. XXXVI. 
''See Doctor Hillebrand's note, p. 39. 
and 
