100 CORUNDUM^ ITS OCCURRENCE AND DISTRIBUTION. 
it. The rock for the most part is in a highly decomposed condition, 
but there are small exposures of the undecomposed rock in many 
places. The gravels in Avhich the rubies are found rest on a soft 
saprolitic rock which is the result of Aveathering of the basic silicate 
rocks in ])lace. By means of shafts and of the workings at the gravel 
washings it has been shown that at a depth of 35 feet or more these 
saprolitic rocks contain fragments of the undecomposed rock and pass 
into such rocks as eclogite-amphibolite and hornblendic gneiss. 
A narrow dike of hornblendic eclogite a few feet in width is 
exposed neni- the present workings of the compan}^ and can be traced 
for about 100 yards. 
No rubies have been found in the undecomposed rock, but at In 
Situ Hill small rubies of a rather pale color were found in a narrow 
band of saprolitic rock. This band Avas, hoAvcA^er, cut off by slick- 
ensides so that it could not be folloAved in any direction. There are 
four parallel slickensides that have been exposed at one place in the 
AAorkings, the general direction of the slickensides being N. 75° E. 
Some of these are 70 feet in length and of unknoAvn depth. It is very 
evident that there has been a great deal of disturbance in this immedi- 
ate vicinity through the breaking of the rock masses by faulting, the 
ready influx of Avater having caused the reduction of the rocks to 
their saprolitic condition. 
In washing the gravels and bodies of saprolitic rock, masses of 
undecomposed rock have been uncovered, and in the center of these 
nodules of the pure hornblende rock have been found. The saprolite 
bordering these nodules often contains particles and crystals of 
corundum. 
Less than 2 miles to the east of In Situ Hill, beyond Belts Gap of 
the CoAvee Mountains, corundum of a gray to bluish color, but highly 
crystallized, lias been found in hornblende-gneiss. One mile a little 
north of west, at the Sheffield mine, pink corundum has been found 
in amphibole-schist. (See pp. 57-59.) 
An association of corundum peculiar to this locality is Avith the 
garnet rhodolite." Corundum and garnet (almandine and rhodolite) 
not only occur constantly together in the saprolitic material and in 
the gravels, but corundum crystals have been found that bear the 
impression of the garnet. By means of wax a mold Avas taken of 
these impressions, and they were shown to be either the dodecahedron 
or trapezohedron. On the other hand, some of the ruby crystals Avhen 
broken are seen to have a rhodolite garnet inclosed, and the garnet 
can often be seen in the transparent ruby crystal and the cut gem. 
The peculiarities which distinguish this garnet from the ordinary 
occurrences of the species are its variety of shades and tints, for the 
« The name rhodolite was selected for this mineral as describing its most prominent 
character, namely, its delicate rose-like color. 
