112 GUIDEBOOK OF THE WESTERN UNITED STATES 
From Collado siding there is a branch railroad south to the Micro- 
lithic quarry, 5 miles distant, where mica and feldspars of various 
colors are obtained from a coarse pegmatitic rock in Carrizo 
Mountain schist of tga age in the northwestern slope of the 
Van Horn Mountains The occurrence of this old rock at this 
place is due to a pailisherlirciaterte fault that brings up a block of 
the schist, Van Horn sandstone (150 feet thick), and limestone of 
Permian age on the west against limestones of Trinity age (Lower 
Cretaceous) on the east. To the south from Dalberg siding and 
vicinity there is a good view down the wide valley between the Van 
Horn and Eagle Mountains to the Rio Grande, 40 miles distant. 
Some years ago there were in this valley ata place about 8 miles 
south of the railroad, some deep cracks in the ground that were 
attributed to an earthquake. They trended north and south and 
cut clays in the arroyo and gravel on the benches. From Collado 
siding to Hot Wells and beyond there are fine views of the high, 
craggy Eagle Mountain to the west, a huge pile of lavas and other 
volcanic rocks of Tertiary age,® in which the highest point is 7,510 
schist, with lenses and veins of quartz 
&nd dikes of dark-green basic intrusive. 
Some of the schists contain garnet. 
The Carrizo Mountains are near the 
center of a large, irre uplift in 
which the strata and underlying erystal- 
taceous to middle Tertiary 
A fault of 300 or 400 feet dis- 
t along the west side of the 
7 The pegmatites at this place pre- 
sent great variety in color and compo- 
sition, and some of the dikes are 100 
feet wide. They range from graphic 
granite, an intimate intergrowth of 
feldspar and quartz, to crystals of feld- 
spar and mica a foot or more in size. 
The feldspar varies in shade from flesh- 
color to pearly white. Large tabular 
masses of black tourmaline occur in 
places and some crystalline hematite. 
The schists are of many kinds; the 
prevailing type is a finely foliated ag- 
gregate of muscovite and flesh-colored 
or white feldspar, but — = ete feld- 
spar, biotite, and garne he aver- 
age general dip of bax foliation ae 
to Asa east, but it swings in various 
directions. There is considerable vert 
quartz, mostly milky whit 
crete blocks and other Socoke cadaan 
materials. 
* The =P rocks of Eagle Moun- 
an irregular 
and 
quartz and amphibole schists, quartz- 
