124 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 
the large zonally built orthoclase phenocrysts. The accessory min- 
erals include titanite, zircon, and apatite. 
The granite is cut by dikes of aplite rather poor in biotite. Peg- 
matite dikes are common. The coarsely granular pegmatite is com- 
posed of feldspar and quartz anhedra which reach a maximum diam- 
eter of L2 inches. Limonite pseudomorphs after pyrite are inclosed in 
both quartz and feldspar grains. Graphic granite, with letters one- 
fourth inch across, is a less common variety of pegmatite. A third 
facies i> an aggregate of coarse feldspar individuals with a few quartz 
anhedra. Embedded in the feldspar are numerous biotite blades from 
one-half to 1 inch long. Under the micro-cope this rock is seen to 
be composed of large plates of microperthitic orthoclase intergrow^j 
with quartz in the manner characteristic of graphic granite. Be- 
tween these large area- i- a granular mosaic of orthoclase and quartz. 
A few needle-like blades of biotite and grains of magnetite are also 
present. 
Next to the limestone the granite becomes line grained, although the 
phenocrysts retain their size and in consequence probably solidifief 
prior to the intrusion of the magma into the limestone. Limonite 
cubes after origins] pyrite are particularly common near the contact 
The limestone near the contact is metamorphosed to a line-drained 
marble of white color, which in some localities contain- lenses oi 
pale-gray marble. In less pure layers fibrous tremolite, locally ir 
globular masses, is developed. Other layers are colored greenish yel- 
low by serpentine and chlorite. The more impure layers are changed 
to grossular garnet, forming a heavy dark-brown rock. This garnel 
in cavities occur- a- beautiful citron-yellow crystals. A heavy roc], 
of deep-green color also proves, on microscopic examination, to Ik 
composed of garnet, which even in thin section ha- a decided greer 
tinge and which i- associated with calcite, staurolite, tremolite, quartz 
zoisite, titanite, and iron ore. Another thin section of altered lime* 
-tone proves to be a finely granular marble, between the calcite grain* 
of which are tremolite and colorless garnet grains and a. few irregu- 
lar area- of chlorite. Still another thin section is composed of large 
plates of calcite and quartz, in which chlorite, tremolite. and color- 
less garnet are micropoikilitically inclosed. The shale of the AVebsi 
conglomerate is metamorphosed to a. slaty -hale, in which ne^t< o: 
tiny muscovite tablets are developed. Other facies contain numerou: 
pyrite crystals. The most interesting metamorphosed shale is a blacl- 
argillite, in which are many rectangular white column- with blacl 
cores. Under the microscope these column- embedded in the carbo 
naceous argillite are seen to be chiastolite, a variety of andalusite 
On its r<\^- this mineral i- somewhat altered to muscovite. 
This coarse granite porphyry, characterized by two generations o: 
mineral solidification and associated with aplitic and pegmatiti< 
