480 GEORGE I. FINLAY 
Creek, seven miles southwest of Canyon City, Colo. The abandoned 
tunnel of the Rocky Mountain Boy bears N14E from it. The dis- 
tance from the mine tunnel is about roo yards. The United States 
landmark No. 6236 has been cut on the vein at the summit of the 
ridge. The vein is from 4o to 80 feet wide. It stands vertically in 
the schist, appearing as a knob where it crosses the divide. It strikes 
N46E, running down the hillside for some distance on either hand 
until it is covered by the rock slide of the lower slopes. Two prospect 
holes have been made on it above the Rocky Mountain Boy. Along 
the south wall against the schist are stains of copper, malachite, and 
it is near this wall that the corundum occurs most abundantly. 
Macroscopic description.—In hand specimens glassy quartz, in 
grains an eighth of an inch across, is the most abundant mineral in 
the pegmatite. The corundum appears to favor association with the 
quartz. White sugary plagioclase is present, with rarer crystals of 
pink microcline. Two kinds of mica are prominent, one white, the 
other black and much more abundant. The plates are at times half 
an inch across. Muscovite and biotite are indicated by the axial 
angles. Corundum appears as a local constituent of the vein in 
hexagonal crystals which are often half an inch in diameter. The 
mineral is glassy, and of a clear blue color, but not good enough to 
be of gem quality. The basal cleavage is prominent. 
Microscopic description.—Under the microscope quartz, with the 
"minute needles referred to rutile, is seen to be as abundant as are the 
feldspars taken together. Microcline, and acid plagioclase, probably 
albite, twinned on the albite law with occasional pericline lamellae, 
are observed. No carlsbad twins were noted. The highest sym- 
metrical extinctions measured were 9°. Muscovite is unusually 
prominent. The corundum resembles glassy quartz. Rectangular 
cleavage cracks parallel to the base are, however, prominent. Nega- 
tive crystals of hematite are often seen in it. Basal sections give a 
uniaxial cross without the rings which appear in the field of view 
when the figure of quartz is examined. Dumortierite occurs in very 
perfect pointed prisms 1™™ in length by 0.03™™ in breadth. They 
are faint blue. At times they make up bundles of radiating needles; 
occasionally they show a parting parallel to (oor). Large, more 
massive columnar aggregates are very strongly pleochroic, from 
