CLAI'.KK.j 
IG1TEOUS AND CRYSTALLINE ROCK! 
14' 
i. HI6HWOOD MOUNTAIN8. 
Rocks collected by W. H. Weed and L. V. Pirsson, who furnish the 
petrographic data. Analyses A to X. inclusive, made in the laboratory 
of the Sheffield Scientific School, under the direction of Professor 
firsson. 
A. Trachy-andesitic breccia, head of north fork of Willow Creek. 
Adamelloxe. Contain- hornblende, biotite, iron ore, apatite, plagio- 
clase, and orthoclase, with a little kaolin and limonite. E. B. Hurl but 
and B. Barnes, analysts. 
B. Trachyte, dike 1 mile north of divide in Highwood Gap. Higk- 
woodose. Contain- 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. Pvlask 
Contains phenocrysts of alkali feldspar, aegirine-augite, and nielanite, 
in a'groundmass of alkali feldspar. Apatite, iron ore, a trace of 
ealcite. and some kaolin are also present. H. W. Foote, analyst. 
D. Trachyte, dike on Aspen Creek. Monzonose. Contain- alkali- 
hornblende and alkali-feldspar phenocry>t>. in a gronndmass 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. Judithme. Contains 
aug'ite. biotite. iron ore. and orthoclase, in a groundmass of alkali 
feldspar: also apatite and some kaolin. AW M. Bradley, analyst 
A. 
b. 
c. 
SiO, c . . . 59. 24 
A1 2 3 13. ^4 
FeA 5.46 
FeO 1.36 
MgO 4. 79 
C3a0 5.60 
Sa_o 3.13 
v." 4.22 
b" 2.02 
no, 22 
?A - 34 
mi« ) trace 
; rO none 
■tO trace 
JO 08 
Mi none 
fa 04 
100.34 
IbO .01 
58.04 
17. 24 
2.49 
1.24 
1.79 
3. 50 
3. .">7 
10.06 
1.95 
. 30 
trace 
andet. 
andet 
trace 
.38 
58 
. 09 
100.33 : 
57. 18 
1<. 54 
- 
1.15 
.69 
2. 31 
4.4^ 
- " - 
2.10 
. 30 
. 0b 
trace 
trace 
.49 
I 
.17 
55.23 
18.31 
4. 90 
1.85 
:;. 62 
4. 02 
6. 43 
1.84 
.42 
. 58 
trace 
trace 
.46 
.23 
none 
_ 
.08 
51.94 
15. 7^ 
4. 07 
3. 71 
3. 4^ 
6. 04 
3.44 
" 
2.17 
.39 
. 59 
trace 
.28 
.42 
. 
a 
a 
. 02 
100. 18 
9 
