Custer weekly chronicle. [volume] (Custer City, S.D.) 1890-1931, 1909-10-02
RARE METALS.
Tin, Tungsten, and Tantalum Deposits o.
South Dakota-by Frank L. Hess.
From Bulletin No $780, Contributions to Eco
nomic Geology, 1908, Part L.

tlffOm Bulletin NO. 0SU, CCuITlDuUlOHS 10 Ec'
nomic Geology, 1908, Part IL
TIN DEPOSITS IN THE ...
SOUTHERN BLACK HILLS
Blue Bird Claim.
The Blue Bird claim is located on
short pegmatlte dixie II miles south Q
Hill City on the north side of smal
stream flowing into Spring Creek, whicl
is nearly mile to the east. The dix
is IA feet wide at the top and dips 6
degrees east. Cassiterite is carried ii
veinlike portions of the dixie, inch T.
% inches wide, composed of muscoyit
and quartz with little feldspar. Th
mica occurs in narrow aggregate up Il
one-half inch wide by II to Il inche
long, partly perpendicular to the in
distinct walls of the veins.
The cassiterite in many places has {
tabular form, but is largely anhedral
having been crystallized contemporane
ously with the other minerals, quartz
mica, and feldspar. Some particles, how
ever, show their crystal form we'll, and
these were probably the first to crystal
lize from the mass. Here and there
crystals which are probably twinned, are
L-shaped. One specimen has legs that
form a right angle and are fiye-six.
teenths and one-half inch long, by about
one-eighth inch thick. The crystal is
broken, 80 that its width is unknown.
At a depth of 40 feet the dixie is
crushed and pinches out through fault
ing, which has taken place since the
solidiication of the dixie. A few feet Of
sinking and of drifting to the east have
not shown the continuation of the dixie.
Olympia Claim.
The Olympia claim, owned by Henry
Petit, is on the south side of the riyulet
near which the Blue Bird claim is sit
uated, but e quarter of mile nearer
Spring Creek. The basis of the claim is
a pegmatite dixie feet thick and several
hundred feet long, with dip of 45 de-
grees to 55 degrees II. AZ degrees west.
The dixie is rather fine.grained and at
one place for thickness of about 6
inches along the hanging wall contains
considerable cassiterite. This portion of
the dixie is composed mostly of feathery
mica and quartz. The mica is in plates
an inch or more long by one-sixteenth
to three -sixteenths inch wide in overlap
ping scales radiating in gently curved
lines from an axis. The cassiterite is
black, partly in tabular forms, reaching
of an inch in length by
one-eighth inch in thickness and little
more in breadth. Most of it is in rather
irregular fiat grains following the lines
of the mica.
The portion bearing cassiterite has
been traced for Is feet. A similar mica
ceous zone is seen along the foot wall in
places, but carries less cassiterite. The
middle part of the dixie seems to contain
little tin. No other accessory minerals
were noticed.
Tin Plate Group.
On the Tin plate group of claims, held
by James Angus and lying between the
Olympia and OrevilIe (6 miles southwest
of Hill City, several pegmatites were
examined, of which some were similar
in structure to the dixie on the Olympia
and others were coarser. Only small
amount of cassterte was seen in any of
the dikes. None of the pegmatite had
been crushed and panned however, and
this treatment will frequently show cas-
siterite in sore quantity where it is
noticeable on the outside Of the
rock.
Sallie Cavanaugh Claim.
On the west side of the summit of a
small hill west of Oreville, a collection
of possibly a score of houses, Mrs. E.
NJ. McDermott has a claim known as
The Sallie Cavanaugh. 1t is on a coarse
pegmatite dixie reaching 25 feet in width
by 500 feet in length and striking N. 10
degrees E., with nearly vertical west
erly dip.
A rich bunch or short shoot of tin ore,
which dips 20-25 degrees n, is exposed
On this claim. The shoot is composed of
coarse mica and quartz, with coarse cas-
,iterite. Some, of the mica plates are
more than 2 inches across, and the cas-.
siterite forms several veinlets one-half
nch wide and foot long. The shoot as
exposed is about feet wide and can be
'een for only or feet. A few feet to
he north another but less rich shoot was
exposed. 1t was of somewhat greater
width. The large, irregular pieces OF
,assiterite which occur in such coarse
pegm atites are not composed of an
aggregate of small crystal individuals
which have grown together, as is the
,ase with many large pieces from veins,
,ut of masses which haye segregated
rom the magmas in the same way as
coarse quartz or mica, and have formed
crystalline individuals either single or
winned.
The dixie is somewhat irregular in
and if shafts were sunk it
would probably be found to pinch in
places The ore shoots as exposed,
hough rich, are not large, and their ex-
ent is uncertain.
IN &c louar o;da tho dila r;coc oO tn
30 feet above the hill slope, and a con-
siderable portion must have been eroded
away. 1t seems probable, therefore,
hat in the stream bed not over 300 feet
below there should be placer which
nay be workable and should carry
coarse cassiterite. "a
Ito be Continued
The moon is called silyery because it