42 CORUNDUM IN THE UNITED STATES. [bull.] 
crystallized, lias been found in hornblende-gneiss. One mile a litt 
north of west, at the Sheffield mine, pink -corundum has been foui 
in amphibole-schist (see pages 31 and 58). 
An association of corundum peculiar to this locality is with tl 
garnet, rhodolite. Corundum and garnet occur not only constant 
together in the saprolitic material and in the gravels, but corundu 
crystals have been found that bear the impression of the garnet. 1; 
means of wax a mold was taken of these impressions, and they wei 
shown to be either the dodecahedron or trapezohedron. Then agai 
some of the ruby crystals when broken are seen to have a garni 
inclosed, and the garnet can often be seen in the transparent rub 
crystal and the cut gem. 
As has been said, there is no limestone in this immediate vicinity 
and these rubies were probably derived from an amphibolite or ech 
gite. The usual flat tabular form of the crystals is one that seem 
to be characteristic of the gem corundum when found in igneous rock 
The Cowee Creek rubies frequently contain inclusions, some o 
which are very minute, known to jewelers as "silk," and these giv 
rise to a cloudiness or sheen in the polished gem. Rutile and menac 
canite often occur in the rubies and greatly mar their beauty and value 
Some gems that were 3 or 4 carats in weight have been cut, whicl 
were free from inclusions, of fine color, and transparent. A grea 
many smaller ones have been cut that are perfect gems. In color an< 
brilliancy these gems are equal to the Burma ruby, and if the per 
centage of the unflawed transparent material increases but little thii 
new field will be a worthy rival to the Burma field. 
A considerable percentage of the transparent material is often verj 
badly flawed by cracks due to parting, and by the inclusions of rutih 
or menaccanite, so that the percentage of perfect stone from this 
mine is small. This, however, is true of the rubies from the Burin? 
field, for a large proportion of the rubies on the market to-day art 
usually' more or less flawed with the parting cracks. 
The pleochroism exhibited by the Cowee rubies is very marked, some 
of them being a very rich pigeon-blood red in the direction of the ver- 
tical axis — that is, looking down upon the basal plane — and changing 
to an almost pinkish- white color when viewed at right angles to this 
or looking through the prism. The pleochroism which nearly all the 
deep-colored varieties of corundum gems exhibit is one of the means 
of identifying a corundum gem; this often interferes with the cutting. 
The ruby crystals ' from the Cowee Valley show a very wide varia- 
tion in their development. Although many of the crystals are so 
striated that no crystallographic measurements were possible on the 
reflecting goniometer, the faces were readily identified by means of 
the contact goniometer. On some of the crystals the faces were bright 
Am. Jour. Sri., 1th series, Vol. VIII, 1899, p. 379. 
