124 ANALYSES OF ROCKS AND MINERALS, 1880—1908. 
B. Pyroxene andesite, Sierra Grande. Tonalose. Contains augite, less hypers- 
thene, microliths of plagioclase, apatite, magnetite, and a smoky-brown glassy base. 
Sp. gr., 2.635, 21° P. R. C. 1335, 
C. Plagioclase basalt, end of San Rafael flow. Camptonose. Contains plagioclase, 
atigite, olivine, with much iddingsite, magnetite, and apatite. Sp. gr., 2.970, 21.5°. 
P. R. C. 1336. 
D. Nepheline basanite, Ciruella. Limburgose. Contains augite, olivine, nephelite, 
plagioclase, magnetite, apatite, and a little biotite. Sp. gr., 3.122, 22° 0.55 per cent 
K,O and 2.10 per cent Na,O soluble in 1:40 nitric acid. P. R. C. 1337. 
4, MISCELLANEOUS ROCKS. 
A. Obsidian, Obsidian Hill camp, Tewan Mountains. Liparose. Described by 
Iddings, 7th Ann., p. 292. A rhyolitic obsidian, containing grains of iron oxide and 
a few microscopic feldspars. Resembles that from Obsidian Cliff in the Yellowstone 
National Park. Analysis by L. G. Eakins, record No. 851. Sp. gr., 2.352, 23.5°. 
B. Trachyte (?), from Los Cerrillos. Described by Diller, Bull. 42, p.39. Analysis 
by F. W. Clarke, record No. 346. Rock composed chiefly of orthoclase, with a con- 
siderable amount of biotite, epidote, pyrite, and limonite, and some amorphous sub- 
stance. It is the matrix or gangue rock of the Los Cerrillos turquois. 
C. Gabbro porphyry, Mount McKensie, Los Cerrillos Mountains. Andose. 
Received from J. F. Kemp. Described by D. W. Johnson, in School of Mines Quart., 
vol. 25, p. 82. Analysis by George Steiger, record No. 2027. Contains augite, plagio- 
clase, orthoclase, and biotite. P. R. C. 1300. 
D. Andesite, Country rock, Bonanza mine, Hillsboro. Shoshonose. Contains 
plagioclase, orthoclase, augite, and hornblende. 
E. Syenite porphyry, Cook’s Peak. Dacose. Contains orthoclase, plagioclase, 
biotite, hornblende, and quartz. Rocks D, E, described by C.H.Gordon. Analyses, 
as yet unpublished, by G. Steiger, record No. 2238. 
F. Quartz syenite, near Merrimac mine, 3 miles east of Organ City, Organ Mountains. 
Contains orthoclase, albite, quartz, biotite, augite, titanite,and magnetite. Descrip- 
tion furnished by W. Lindgren. Analysis by Steiger, No. 2371. 
