122 
ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [but.l.182. 
altered rock, as determined on considerable fragments, should be to 
each other approximately as 100 is to 86 (i. e., to 100 less the loss of 
substance due to metamorphism). The specific gravities as actually 
determined are 2.764 and 2.734, and their ratio is as 100 to 99. This 
result does not accord with the idea that the loss of substance has 
resulted in corresponding increase of porosity with retention of initial 
volume. In so far as the laboratory determinations of specific gravity 
may be relied upon in drawing conclusions as to the mass as a whole, 
they indicate that the loss of substance has been followed by diminu- 
tion of volume, presumably associated with actual cracking or Assur- 
ing and not with increased porosity. 
Analyses and recalculations of rocks of Polar Star mine, Engineer Mountain. 
Constituent. 
I. 
II. 
Ha. 
Loss or gain 
of each con- 
stituent in 
percentage 
of the whole 
original 
rock. 
11/). 
Loss or gain 
of each con- 
stituent in 
percentage 
of the whole 
original 
rock. 
SiOo 
Per cent. 
55. 61 
16.40 
5. 44 
2.37 
3. 25 
5. 85 
2.61 
3. 77 
.46 
1.51 
1.10 
1.33 
.45 
Trace. 
None. 
None. 
. 09 
.03 
.05 
Trace. 
Per cent. 
64.79 
18.93 
None. 
None. 
None. 
.43 
.15 
.24 
.50 
5.39 
1.21 
None. 
.51 
Per cent. 
56. 13 
16.40 
None. 
None. 
None. 
.37 
.13 
.20 
.43 
4.66 
1.04 
Per cent. 
+0. 52 

-5. 44 
-2. 37 
-3. 25 
— 5.48 
-2.48 
-3.57 
- .03 
+3.15 
- .06 
-1.33 
- .01 
Percent. 
64. 14 
18.74 
None. 
None. 
None. 
.42 
.14 
23 
.49 
5.33 
1. 19 
Per cent. 
+8. 53 
A1 2 3 
+2.34 
Feo0 3 
-5.44 
FeO 
MgO 
-2.37 
-3.25 
CaO 
- 5. 43 
Na.»0 
-2.47 
K 2 
-3.54 
HoO- 
.03 
HoO+ 
:;. 82 
TiO» 
. 1 >;* 
co 2 - 
-1.88 
Po0 5 
.44 
. 50 
+ .05 
s 
Cro0 3 
None. 
None. 
None. 
.06 
Trace. 
Str.tr. 
7.19 
NiO 
MnO 
— .09 
+ .02 
- .05 
- .09 
BaO 
SrO 
.05 
.06 
+ .03 
- .05 
LioO 
FeSo 
+6.22 
7.12 
7 1" 
Total 
100.32 
2. 764 
99. 40 
-14.25 
°C. (W. F. 
-1.96 
Sp. gr 
2. 734 at 19 
Hillebranrl-^ 
I. Latite. Country rock of the Polar Star mine, Engineer Mountain. Analysis by H. N. 
Stokes. 
II. Me tasoinatically altered latite. Wall rock of Polar Star mine, Engineer Mountain. Analy- 
sis by H. N. Stokes. 
Ha. Recalculation of II on basis of constant alumina. 
116. Recalculation of II on basis of constant volume. 
It will be remembered that the preceding discussion rests upon the 
initial assumption that the alumina has remained constant during the 
metamorphism. This assumption may not be correct, and it will 
further the inquiry, as well as illustrate the complexity of the problem, 
