IGNEOUS AND CRYSTALLINE ROCKS. 115 
12, TELLURIDE QUADRANGLE. 
Rocks collected by Whitman Cross. All except A described in Folio 57. 
A. Lamprophyre, allied to camptonite, Black Face. Andose. Consists of a fine | 
felt of plagioclase, augite, and brown hornblende microlites, with flakes of biotite, and 
a cryptocrystalline part, which is probably in large degree orthoclase. Some magne- 
tite and apatite. Analysis by Hillebrand, record No. 1719. Sp. gr., 2.783, 22° P. 
R. ©. 1282. 
B. Quartz monzonite, northeast of San Miguel Peak. Toscanose. Contains ortho- 
clase and plagioclase in about equal amounts, with abundant quartz and much Jess 
augite, hornblende, biotite, magnetite, and apatite. Analysis by H. N. Stokes, record 
No. 1764. Sp. gr., 2.720, 34° Described by Cross in 21st Ann., pt. 2. P. R.C, 1279. 
C. Diorite monzonite, Ophir Needles. Tonalose. Contains abundant labradorite, 
with augite, hypersthene, biotite, orthoclase, magnetite, apatite, and a very little 
quartz. Analysis by Stokes, record No. 1764. Sp. gr., 2.860, 33° 
D. Gabbro porphyry, pass south of Mount Sneffels. .Andose. Contains numerous 
phenocrysts of labradorite or bytownite, in a groundmass of plagioclase, orthoclase (?), 
augite, hypersthene, biotite, magnetite, and apatite. Analysis by Stokes, record No. 
1764. Sp. gr., 2.949, 26.56° P. R. C. 1280. 
E. Vitrophyre, ridge east‘of Windy Gap. Yellowstonose-lassenose. P. R.C. 1281. 
Analysis by H. N. Stokes. 
F. Gabbro, Stony Mountain, Ouray County. Hessose. Analyzed by Eakins in the 
Denver laboratory. Sp. gr., 2.891, 13.5°. P. R. C. 199. 
af 
Bw 
- 
& 
Ry 
47.32 | 64.72 | 52.05 
16.71 | 14.18] 17.96 
6.92| 158] 4.09 
5.941 140] 6.33 
5.69 | 150] 5.03 
851} 2.62] 8.64 
2.70} 3.88] 2.99 
2.02) 1.82 161 
e 6 
tod] want  °9? 
99.95 | 100.20 | 100.41 
13. MISCELLANEOUS ROCKS. 
A. Diabase, east of the Sugar Loaf, Boulder County. Hessose. Description fur- 
nished by Whitman Cross. The rock contains labradorite, orthoclase, augite, and 
magnetite, with small amounts of hornblende, biotite, apatite, and secondary chlo- 
rite. Sp. gr., 3.027, 21° P. R.. 166. 
B. Pyroxene separated from A. Analyses A, B, made by L. G. Eakins in the 
Denver laboratory. 
C. Alkali syenite porphyry, Idaho Springs. Pulaskose. Described by S. H. 
Ball, in P. P. 63. Contains anorthoclase, orthoclase, egirine-augite, garnet, titanite, 
biotite, apatite, magnetite, and often zircon. Analysis by G. Steiger, record No. 
2258. 
D. Porphyry, Idaho Springs. 
E. Biotite latite, Idaho Springs. Rocks D, E, received from J. E. Spurr, but 
without description. Analyses by W. T. Schaller, record No, 2263, 
