130 ANALYSES OF ROCKS AND MINERALS, 1880-1908. 
Rocks G to M were also collected by Spurr. Analyses L, M by W. F. Hillebrand, 
record No. 2087; the others by George Steiger, No. 2088. 
G. Early andesite, hanging wall of vein, 300-foot level, Mizpah mine. A more 
advanced stage of quartz-muscovite alteration than F. 
H. Extreme stage of alteration of andesite to quartz and muscovite, west drift, 
Mizpah vein. Quartz, with much muscovite. 
I. Augite-biotite andesite, Mizpah extension shaft. Contains phenocrysts of plagio- 
clase and augite, with some alteration to calcite and serpentine. 
J. Pyroxene-biotite andesite, completely decomposed. Montana-Tonopah shaft. 
Feldspars entirely altered to calcite, sericite, and quartz. Biotite and hornblende 
altered to chlorite, calcite, quartz, sericite, siderite, and pyrite. 
K. Biotite dacite, north side of Mount Brougher. Toscanose. Contains plagioclase, 
possibly orthoclase, biotite, and a glassy groundmass, 
L. Biotite andesite, Halifax shaft. Harzose. Contains plagioclase, biotite, augite, 
and magnetite. 
M. Biotite-pyroxene andesite, North Star shaft. Entirely altered. Feldspar 
altered to calcite. Pyrite, siderite, and rutile are present. 
2. GOLDFIELD DISTRICT. 
Rocks collected by F. L. Ransome, who supplies the petrographic data. Analyses 
by G. Steiger, record Nos. 2249, 2253, 2339. 
A. Altered rhyolite, east slope of Vindicator Mountain. Contains quartz, alunite, 
calcite, and sericite, with a small amount of undeterminable material. 
B. Pyroxene-hornblende andesite, first hill northwest of Vindicator Mountain. 
Tonalose, near yellowstonose. Contains labradorite, augite, orthorhombic pyroxene, 
hornblende, magnetite, and apatite, in a glassy base. 
C. Hornblende-pyroxene andesite, 2 miles northeast of Black Butte. Tonalose. 
Contains plagioclase, augite, enstatite or bronzite, hornblende, and magnetite, in a 
glassy groundmass. 
D. Hornblende-biotite andesite, 1 mile northeast of Black Butte. Améatose, near 
yellowstonose. Contains labradorite, hornblende, and biotite, in a glassy groundmass 
with specks of magnetite. 
E. Pyroxene-hornblende andesite, 1 mile northeast of Columbia Mountain. Tona- 
Jose. Contains labradorite, augite, hypersthene, magnetite, apatite, and glass. Traces 
of secondary calcite and chlorite. 
