CLARKE.] 
IGNKOUS AND CRYSTALLINE ROCKS. 
131 
6. HIGHWOOD MOUNTAINS. 
Rocks collected by W . H. Weed and L. V. Pirsson, who furnish the 
petrographic data. Analyses made in the laboratory of the Sheffield 
Scientific School, under the direction of Professor Pirsson. 
A. Trachv-andesitic breccia, head of north fork of Willow Creek. 
Contains hornblende, biotite, iron ore, apatite, plagioclase, and ortho- 
clase, with a little kaolin and liinonite. E. B. Hurlbut and B. Barnes, 
analysts. 
B. Trachyte, dike 1 mile north of divide in Highwood Cap. Con- 
tains abundant phenocrysts of orthoclase and augite in a groundmass 
of the same minerals; also a little biotite, apatite, and iron ore, and 
some secondary kaolin. E. B. Hurlbut, analyst. 
C. Trachyte, dike north end of South Mountain. Contains pheno- 
crysts of alkali feldspar, aBgirine-augite, and melanite, in a ground- 
mass of alkali feldspar. Apatite, iron ore, a trace of calcite, and some 
1 kaolin are also present. H. W. Foote, analyst. 
D. Trachyte, dike on Aspen Creek. Contains alkali-hornblende 
and alkali-feldspar phenocrysts, in a groundmass of alkali feldspars; 
also some apatite and iron ore. Rock stained by limonite. H. W. 
Foote, analyst. 
E. Trachyte, dike at head of Shonkin Creek. Contains augite, 
biotite, iron ore, and orthoclase, in a groundmass of alkali feldspart 
also apatite and some kaolin. W. M. Bradley, analyst. 
A. 
B. 
C. 
D. 
E. 
Si0 2 
59.24 
13.84 
5.46 
1.36 
4.79 
5.60 
3. 13 
4.22 
2.02 
.22 
.34 
trace 
none 
trace 
.08 
none 
.04 
58.04 
17.24 
2.49 
1.24 
1.79 
3.50 
3.37 
10.06 
1.95 
.30 
.22 
trace 
undet 
undet 
trace 
57.18 
18.54 
3.65 
1.15 
.69 
2.31 
4.48 
8.58 
2.10 
.30 
.05 
trace 
trace 
.49 
.06 
55. 23 
18.31 
4.90 
2.06 
1.85 
3.62 
4.02 
6.43 
1.84 
.42 
.58 
trace 
trace 
.46 
.23 
none 
.32 
51.94 
15. 78 
4.07 
3.17 
3.48 
6.04 
3.44 
7.69 
2.17 
.39 
.59 
trace 
.28 
.42 
.29 
A1 2 3 
Fe.,0, 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 
Ti0 2 
P 2 5 
MnO 
SrO 
BaO 
S0 3 
co 2 
CI 
.38 
.77 
.08 
LecsO 
100. 34 
.01 
100. 58 
.09 
100. 35 
.17 
100. 27 
.08 
99. 83 
.02 
100. 33 
100.49 
100. 18 
100. 19 
99.81 
