38 SLATE DEPOSITS AND INDUSTRY OF UNITED STATES. ' 
these along the cleavage, which dips only about 12°. These analyses, when com- 
pared with analysis A of fresh black slate from the Slatington quarries (see p. 84), 
14 miles farther north-northeast, show a probable loss of 4 per cent of CaO during 
a still earlier stage of weathering. 
Analyses of weathered slates from Pennsylvania, 
SiOo (silica) 
A1. 2 3 (alumina) 
P 2 5 (phosphoric oxide) 
Fe 2 3 (ferric oxide) 
FeO (ferrous oxide) 
MgO (magnesia) 
CaO (lime) 
Na 2 (soda) 
K 2 (potassa) 
H 2 (water)a 
Ti0 2 (titanium dioxide) 
C0 2 (carbon dioxide) . . . 
S (sulphur) 
A. 
Per cent. 
65.56 
17.06 
1.31 
1.00 
.20 
.20 
.26 
.27 
3.81 
4.32 
7.09 
5.33 
.68 
.77 
None. 
None. 
.62- 
.04 FeS 2 
100. 18 
Per cent. 
68.81 
3.14 
100.2S 
a Including carbonaceous matter. 
A thin section of another specimen from the same ledge, made across both dark 
and light parts, shows under the microscope: 
1. Absence of carbonate in both, this having been previously dissolved out. 
2. Many spherules of pyrite in the dark part, some of which, altered to limonite, 
still remain in the white part. 
3. Quartz grains, equally numerous in both. 
4. Muscovite (sericite) much more conspicuous in the light than in the dark part. 
To the above data should be added two analyses of white "shale clays," by Doctor 
Hillebrand, which are regarded as the residual product of the weathering of the 
black slate. 
Analyses of shale clays from Lehigh County, Pa, 
Si0 2 (silica) 
Al 2 3 (alumina) 
Fe 2 3 and FeO (ferric and ferrous oxide) 
MgO (magnesia) 
CaO (lime) 
Na 2 (soda) 
K 2 (potassa) 
H 2 (water above and below 11 0° C. ) . . . . 
Ti0 2 (titanium dioxide) 
100. 23 
Per cent. 
Per cent. 
64.50 
75.77 
a 21. 67 
M5.30 
1.83 
1.09 
.81 
.18 
.20 
.20 
Trace. 
4.26 
2. 85 
c5.65 
4.69 
.85 
.36 
a Including P 2 5 . 
b With trace of Fe 2 3 and (perhaps) P 2 5 . 
Ignition loss. 
C. White "shale clay" quarried for fire clay a half mile south of Fogelsville, Upper Macungie, 
Lehigh County, Pa. 
D. W T hite "shale clay" associated with limonite one-fourth mile northwest of Guth Station, 
South Whitehall, Lehigh County, Pa. 
