FERGUSON AND TURGEON: HARNEY GRANITE. 2. 
The Algonkian.— On the north side of the upper part of the gulch 
referred to in the passage just quoted, (this gulch is three quarters of 
a mile below the railroad bridge on Whitewood Creek, east side), 
occurs an outcrop of Algonkian schist and granite. This outcrop lies 
two-thirds of a mile S. W. of Whitewood Peak (Plate 1). It is about 
70 feet in thickness and consists of schist with two small granite sills. 
It rests directly on the porphyry and, although the upper contact can- 
not be seen, it is to all appearances overlain unconformably by the 
Cambrian. The lamination of this schist dips about 20° S 70° E. 
The schist as seen in the hand specimen is a dark green, brilliantly 
glistening fibrous rock composed of amphibole (actinolite ?) and 
quartz. It has a banded structure, small light colored quartz bands, 
about 4 inch across, alternating with the broader dark bands. None 
of the metamorphic rocks of the Algonkian in the vicinity of Deadwood 
and Lead, as described by Irving (a., b.) and Van Hise, appear to 
resemble this schist. 
The granite is of greater interest as this appears to be the only out- 
crop in the Deadwood region and moreover suggests the presence of 
the base of the Algonkian, if, as seems to be the case, the Harney 
granite is intruded only into the lower schists of the Algonkian. As 
here exposed, it is a coarse pegmatitic rock, its principal constituents 
being large feldspars, apparently albite, with patches of black tour- 
maline. (Hovey.) Quartz occurs both as segregated patches and 
in graphic structure in the feldspar. There is also a considerable 
quantity of muscovite. The following description, by Newton, 
(Newton & Jenney, p. 69) of the Harney granite is equally applica- 
ble to this rock:— 
“Tt is granite on a large scale, with all the elements of that rock — 
feldspar, quartz, and mica — present, but instead of their being mixed 
with tolerable uniformity throughout the mass each constituent. is 
very highly crystalline and aggregated by itself. Feldspar is the most 
abundant constituent and forms 70 or 75 per cent of the whole. It is 
always highly crystalline and sometimes exhibits large crystal faces 
but no perfect erystal was discovered. * * * The quartz of the granite 
is commonly glassy and clear, but its variation in texture and color is 
great. It is usually crystalline, but no crystals are found. * * * It 
composes approximately about 20 per cent of the granite, but is 
distributed with great irregularity. In many cases the quartz pene- 
trates the feldspar mass in irregular seams or fragments, which on 
certain fracture planes produce the figures so suggestive of oriental 
inscriptions, and which have given to the variety its name of graphic 
granite.” * * * 
