24 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.60 



approximately the angles of epidote, which suggested that it might 

 be allanite. A crystal was accordingly crushed and embedded in an 

 oil having an index of refraction of 1.695 and examined with a 

 petrographic microscope, when it was found to be doubly refracting 

 almost throughout and distinctly pleochroic in tones of pale dirty 

 brownish green and greenish black. Its ii.dices of refraction were 

 all distinctly lower than that of the oil, suggesting that the mineral 

 was allanite (??=!. 68 Larsen) rather than epidote (?i=1.73-1.77 Lar- 

 sen). Since the identity and orientation of the crystal were not sus- 

 pected when it was measured, the direction of elongation was 

 mounted as polar. The angles measured are given below as inter- 

 facial angles. 



Angles of allanite crystal from Camas County (fig. 28). 



RUTILE. 



Common red-black to deep-red rutile is unusually rare in these 

 sands, the titanium being present mainly as ilmenite, with some 

 titanite. Rare rounded prisms of deep-red rutile were found in a 

 sand from Rhodes Creek, near Pierce City, and in a Snake River 

 sand from Minidoka. A steely-lustered prismatic crystal 6 mm. long, 

 found in the polycrase-bearing sand from Centerville, was identified 

 as rutile. The prismatic zone is deeply striated, the forms present 

 being a(lOO), 7/i(110), and ^(130). The crystal is terminated by the 

 pyramid e(Oll). This crystal is shown in the drawing (fig. 23). 

 It was peculiar in showing greenish internal reflections and when 

 the crystal was crushed and examined in transmitted light the color 

 was yellowish green, a very unusual color for rutile. As empha- 

 sized under " zircon," some of the light-colored crystals Avhich have 

 been described as that mineral may be rutile, the angles of rutile 

 and zircon being so similar that very accurate measurements are 

 necessary to distinguish between them. 



AUGITE. 



Augite is common in all of the Snake River sands examined and 

 also occurs in lesser amount in several samples from Clearwater and 

 Nez Perce Counties. It was not found in anv of the sands from the 



