Custer weekly chronicle. [volume] (Custer City, S.D.) 1890-1931, 1909-09-25

1t is probable that this dixie is typical o
most of the dikes of the region and tha
the phenomena which accompany i
will be found more or less characteristic
Of others.
The dixie was probably injected be
tween the folle of the schists in pasty
condition, and the stresses developed
through its being forced into place wert
not equal at all points, SO that here and
there the schists forming the sides o.
the dixie were pressed almost together
and in places met, squeezing out the
pegmatite for some distance. This left
the dixie in irregular lens-shaped bodies
The different phases are excellently
shown in the Gertie workings. and g
good illustration of the phase in which
the dixie is wholly parted was printed in
an article by Arthur ]. Morse.
That the squeezing took place before the
crystillization ard soiidification of the
dixie was completed is shown by the fact
that there is no noticeable distortion or
crushing of the crystals.
The pegmatite, like all the pegmatites
of the region, is light colored and fine
grained through most of the dixie. The
feldspar is probably albite 10 the main,
though thorough examination has not
been made. The mica is muscovite and
is peculiarly clear. In places the small
books are almost as transparent as
quartz, showing that there has been
little or no bending or crushing of the
rock since the crystallization of the MIN
erals. Cassiterite and tourmaline occur
In small amount as accessory minerals.
No others are visible in the specimens
collected, beyond few small bright
stains in the muscovite and few rust
stains. The dixie is in places "frozen"
to the walls and sillification extends in
to the schist an inch or more.
The cassiterite is dark brown in thin
section, but appears to be black in the
rock. The particles are of irregular
shape, but tend to elongated tabular
forms which vary in size with the text
ure of the pegmatite. In the fine-gralned
portions of the dixie the cassiterite is in
minute particles which may be barely
visible. In the coarser portions of the
dixie the particles reach an inch in
length, three-eighths of an inch in
thickness, and two-thirds of an inch in
width. So far as seen, the tourmaline
is also black, and being in small parti-
cles 1t is with difficulty distinguished
from cassiterite. 1t does not seem to
accompany the cassiterite in the coarser
parts of the dixie, but occurs in the finer
grained parts, which makes distinguish
ment more difficult, particularly as the
crystals are short and those
of cassiterite are elongated as compared
with the usual habit of these minerals.
The cassiterite occurs in shoots, which
are apparently not very continuous in
any direction, and no rules are known
for their occurrence. In this dixie, as in
other tin-bearing pegmatites of the
region, many parts seem to be practi-
cally barren Of tin.
The rock is easily crushed, and aside
from the saving of slimed cassiterite
probably the greatest difficulty in hand
ling the ore arises from the large amount
of mica it contains. A small mill and
smelter plant, besides shaft-houses, en-
gines, pumps, and air compressor, have
been erected.
tn he Continund