110 CORUNDUM, ITS OCCUKRENCE AND DISTRIBUTION. 
miles to the northeast. From these sapphire deposits stones o: 
deeper colors have been obtained. Those from the first two are o: 
all colors from blue to red, and those from the last are all blue. 
ROCK CREEK. 
For information concerning the sapphire deposits of Rock C^reek " 
am indebted to Mr. William Knuth, of Helena. All the sapphire 
that have thus far been found in this section are in the gravel deposit 
on the West Fork of Rock or Stony Creek, in the southern part o 
(Iranite County, about 25 miles southwest of Philipsburg, the count; 
seat, and 30 miles nearly Avest of Anaconda, Deerlodge County 
(PI. VL) ^ 
The sapphires are found in a rather limited area, which is bounde( 
roughly by the gravels of Cold Creek, Myers Creek, tributaries of th 
West Fork of Rock Creek, and that portion of Rock Creek lyin^ 
between them. 
These gravels were extensively worked during the summers of 1891 
and 1900, pi'incipally by Messrs. William Knuth, of Helena, an( 
William MofRtt, of Philipsburg. Altogether about 100,000 carat 
of rough sapphires were obtained. Of these about 25,000 carats ar 
fit for cutting. In color they are much more varied than those f roi] 
the Missouri River bars, and the prevailing color, which is greenisj 
to bluish green, is deeper. No deep-blue sapphires like the orienta 
stones have been found, but paler blue ones have been obtained, froii 
w^hich very handsome sapphires 2 or 3 carats in weight have b?en cul 
Some of the finest yellow sapphires (oriental topaz) that I have eve 
seen have been found at Rock Creek. One of these weighed nearly 
carats when cut. Pale green and bluish green are among the com 
mon stones, some cutting gems of 5 to 8 carats in Aveight. A numbe 
of beautiful pink sapphires have also been found. 
Few red and ruby-colored crystals have been found, and none tha 
would cut a gem over^i twelfth of a carat in weight. These colors ar 
extremely rare in the Montana sapphire deposits. 
The crystals and fragments of sai)phires that are found in the& 
gravels do not show as much abrasion as those from the Missoui 
River, probably because they have been carried a shorter distant 
from Avhere they originated. 
In habit the crystals are very similar to those already describe 
from the Missouri River, and fig. 16 will also illustrate very Avell th 
character of the Rock Creek crystals. One type that is very notice 
able is a short prismatic crystal whose diameter nearly equals il 
length. A parallel groAvth on the basal plane is only occasicmall 
observed, jnid is composed of the basal plane and imit rhombohedroi 
No sappliires have as yet been found in place, but a few have bee 
