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686 MINERAL RESOURCES, 1913—PART II.
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this
pocket contained much red clay with some of the crystals loose in the
clay. The walls were crumbling and soft with no crystals left attached.
A few small colorless topaz crystals were found on the dump at the time
of examination. These crystals were long and slender, measuring less
than a centimeter in thickness The prospect is reported to have yielded
many transparent finely tinted bluish-green crystals. The pit to the
southwest was made on a small vein of pegmatite 1 to 3 inches thick,
cutting the granite in a N. 70° E. direction, but apparently little
topaz was found The pegmatite vein was traced over 100 feet toward the
main working. Four other prospects were opened on the Bishop place and
good topaz is reported to have been found at some of them.
The
topaz prospect of Sam Await is in low ground between the forks of a dry
wash about 250 yards southeast of the house. About a dozen prospect
pits have been made within an area 125 feet wide and 200 feet long
eastr-northeast. The pits are irregular in shape and none of them are
more than 25 feet across or 8 feet deep. The presence of water within a
few feet of the surface made more difficult the working of the
prospects. They are in part in gravel beds, but chiefly in deposits of
pegmatite, which, with the coarse granite country rock, form a floor
over part of the flat. No definite structure or relation between the
pegmatite and the granite was observed, and the impression gained was
that the pegmatite occurs as irregular masses developed around
miarolitic cavities in the granite. The workings are scattered and it
could not be ascertained whether the pegmatite exposed in each is all
part of one flat-lving sheet or consists of a number of disconnected
masses in a nearly horizontal zone. In the largest pit the pegmatite
exposed ranges from a few inches to nearly 4 feet in thickness, and the
deposit dips about 10° S. The texture of the pegmatite in this pit is
coarse, and pockets were opened which measured over 3 feet across and 1
foot high. Besides massive quartz and microcline feldspar, rough
crystals of each measuring as much as 1 foot across were found
projecting from the walls of the cavities. Most of the quartz crystals
had drusy surfaces but were transparent within. They were colorless to
smoky, and some contained inclusions of many small cavities with or
without bubbles. Most of the feldspar crystals were red, but some of a
gray and pale bluish-green amazon stone variety were observed. A little
black tourmaline in long acicular crystals was associated with the
quartz,
E
enetrating some of
the crystals in many directions. No topaz had een left exposed in the
matrix at this prospect. In another pit 200 feet to the northeast the
topaz-bearing rock is
K
eculiar and different
from that observed at the other prospects in [ason County. The pit
exposed a large mass of fine red felsitic rock through which were
scattered red, gray, and greenish microcline, radiated groups or tuffs
of clevelandite, colorless and smoky quartz, muscovite, and topaz crystals. The felsitic rock is dense grained and composed chiefly of feldspar, quartz, and fine needles of black tourmaline. It appears to be molded around the larger^ crystals of quartz
and other minerals, in some cases showing a partial banding parallel to
their surfaces. The microcline, quartz, muscovite, and topaz are in
crystals of varying degrees of perfection. All are frozen in the
felsitic rock and are generally badly fractured by attemps to separate
them. The radial groups of clevelandite measure several
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