DESCRIPTION OP THE COLLECTION. 
107 
tals ; it is interleaved in fragmentary films between tbe masses of feldspar. No dark mica or 
any hornblende is visible in the specimen. 
No. 7. Canon San Antonio. —In composition this specimen simulates No. 6, but differs from 
it in its texture, and in the .color of the mica, which in this is dark and in larger quantity. 
It contains both white and flesh-red feldspar in nearly equal quantities, but quartz is almost 
entirely absent. The minerals are all intimately mingled, and in consequence the mass presents 
a very even grain. The white feldspar is principally in imperfectly-formed crystals, giving a 
porpliyritic character and appearance to the rock. The predominant color of this rock is pink 
from the feldspar, and it is well suited to building purposes. 
No. 8. Canon of San Antonio. —This rock is similar to No. 7, and appears to have been taken 
from the same outcrop. It, however, contains a large crystal of white feldspar, and has a 
distinctly defined linear arrangement of the minerals approaching that of gneiss. 
No. 9. Aquarius mountains, camp before Cactus Pass. —This is a rose-colored granite, compact 
and even in its texture, with a good grain, and suitable for building purposes. The feldspar is 
red or reddish, especially the outer parts of the crystals. The mica is dark-colored, and is not 
in distinct crystals, but is evenly distributed through the mass. 
No. 10. From the same locality as No. 9 ; appears similar, but is somewhat lighter in color, 
and the weathered surface shows the presence of two varieties of feldspar. 
No. 11. Summit of Cactus Pass, Aquarius mountains. —This specimen consists of coarse crys¬ 
talline masses of a brilliant red feldspar, and white, translucent quartz. A little dark mica is 
also seen. 
No. 12. Cactus Pass, Aquarius mountains. —This specimen corresponds with what is usually 
called gneiss. It consists of mica and small white feldspathic grains, ranged in parallel layers. 
The mass has the appearance of a metamorpliic rock. 
No. 13. Aquarius mountains. —A fragment of granite traversed by veins of compact epidote. 
No. 14. Cerbat mountains, Bill Williams’ fork. —This is a beautiful flesh-colored granite. 
The mica is distributed in detached crystalline grains, and being very dark and compact, re¬ 
sembles hornblende, and gives the rock a strong resemblance to sienite. The quartz of the 
specimen is amethystine and rose-colored, and the feldspar is reddish, translucent, and in crys¬ 
talline grains, presenting a porphyritic character. 
No. 15. Bill Williams’ fork. —A coarse-grained sienitic granite. The feldspar is in large 
reddish imperfectly-formed crystals, and the hornblende is dark-colored but not abundant. 
No. 16. Mouth of Big Sandy creek , (Bill Williams’ fork of the Colorado.) —This specimen is 
a coarse-grained porphyritic granite, with large imperfect crystals of a rose-colored feldspar. It 
contains also a lighter-colored variety, in small quantity, and a dark-colored mica. 
No. 17. Cerbat mountains, on Bill Williams’ fork. —This is a dark, reddish-brown rock, in 
which the mineral characters are not well defined. It is micaceous and contains white grains, 
which are probably feldspar. This mineral, with the mica, is evidently arranged in parallel 
layers, and the rock is gneissose, and probably metamorpliic. 
No. 18. Near the mouth of the Bill Williams’ fork of the Colorado. —A compact dark-red 
granite, highly ferruginous, and not presenting an even, clear grain. It has the appearance of 
a weathered specimen stained by iron. (No. 35 is a similar rock from the same locality.) 
No. 19. Bill Williams’ fork of the Colorado. —A dark-green metamorpliic rock, with a quartz 
vein running parallel with the structural lines of the rock. Grains and threads of similar 
white opaque quartz are also seen running in parallel lines through other parts of the mass. 
The green color appears to be due to chlorite, or green mica. The mass emits a strong argilla¬ 
ceous odor when it is moistened by the breath. 
No. 20. Bill Williams’ fork, near its mouth. —This specimen bears a general resemblance to 
No. 19, but the minerals in this are more distinct, while in the other they are not separately 
defined. The structural character of this rock is at once apparent, and the mass cleaves more 
