296 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



BOISE COUNTY 



In Boise County and many of the adjacent counties the heavy 

 residues from placer gold washing operations contain abundant gar- 

 net ranging from fine sand to rounded pebbles the size of a walnut. 

 These are deep red in color and many of them are of gem quality. 

 All of these are brownish-red in color, no distinctly rose red ones hav- 

 ing been seen. A specimen of coarse concentrate from Centerville 

 contains numerous such garnets. One bright red trapezohedral 

 crystal 4 mm. in diameter has an index of refraction between 1.80 

 and 1.82 as has a brownish red irregular fragment from the same lot. 

 A bright brownish-red trapezohedral crystal had an index very close 

 to 1.815. A lot of 50 small garnets uniformly 1 mm. in diameter 

 were crushed and examined. These came from a concentrate from 

 the Boston-Idaho dredge, Idaho City. The color was brownish red. 

 The garnet of this lot is colorless in section, isotropic, and varies in 

 refractive index from 1.810 to 1.815. 



BINGHAM COUNTY 



A sample of heavy concentrate from fine Snake River sand from 

 a placer mine at Rosa, Bingham County, contains occasional grains 

 of brown-red garnet. 



CAMAS COUNTY 



A sample of placer concentrate from Bear Creek, Camas County,, 

 contains common minute sharp crystals of brown-red garnet. 



CLEARWATER COUNTY 



Red garnet, mainly of the purplish shade indicative of a notable 

 content of spessartite, occurs commonly in the heavy residues from 

 gravels worked for gold, in various localities in Clearwater County. 

 A sample labeled as from Cow Creek, Pierce district, contains fairly 

 large grains and crystals, all of which have a purplish or rose-red 

 color. One trapezohedral crystal from this lot of purplish-red color, 

 3 mm. in diameter, has a refractive index of 1.807. Another irregular 

 fragment of about the same size and color has an index of 1.815. 

 All the garnet of this sample is about the same in color and refractive 

 index. 



A sample of coarse garnet in the Museum collection (Cat. No. 

 87508, U.S.N.M.) from Clearwater County consists of a large num- 

 ber of pieces of various colors. A number of these were examined. 

 The colors are either brown red to reddish brown and black, or rose- 

 red to purplish red. A rough black trapezohedron 2 cm. in diameter 

 gave a brownish powder when ground in a mortar. Under the micro- 

 scope the grains were colorless, transparent, and isotropic, but there 

 is a sprinkling of brown iron-stained material, indicating that the 

 color observed in the hand specimen is due to staining. The index 



