28 PROCEEDINGS OF THE NATIONAL, MUSEUM. vol.60 



HORNBLENDE. 



Although also a lighter constituent which is usually eliminated 

 in concentrating, hornblende is occasionally present in the heavy 

 concentrates. The mineral is usually in imperfect pale green pris- 

 matic forms which have an opaque weathered and frayed appear- 

 ance. Fresher greenish-black cleavages of hornblende were noted 

 in some samples, especially in Snake River sands from Wapi and 

 Minidoka. 



CORUNDUM. 



Corundum is a mineral which has probably been removed from 

 the sands by screening, as it ordinarily occurs in crystals much 

 larger than the average grain of the sands and owing to its hardness 

 and tenacity it is seldom reduced to small size by wear. This mineral 

 was noted only as one or two crystals having the form of rounded 

 hexagonal tablets in the sand from Rosa, Bingham County. Corun- 

 dum is known to be common in many gold-bearing gravel deposits 

 in the region around Pierce City and near Resort, in Idaho County. 

 A placer mine near Meadows, in Washington County, has also yielded 

 numerous crystals of corundum, some of gem quality. Specimens 

 of corundum from Resort which are preserved in the United States 

 National Museum are rough hexagonal crystals up to 1 inch in 

 diameter having gray to blue and lavender colors. One crystal is 

 tabular and brown in color with a bronzy metalloidal sheen. 



CHALCOPYRITE. 



Chalcopyrite was found as angular grains in a sand from Wapi on 

 the Snake River. The broken fragments are without definite form 

 and they all have a thin translucent enamel-like coating of some dull 

 green material which resembles a colloidal iron silicate rather than 

 an oxy-compound of copper. Broken irregular grains of chalcopyrite 

 occur also in the radioactive samarsldte concentrates from Idaho City. 



OBSIDIAN. 



While not a mineral, volcanic glass deserves mention as one of 

 constant though not abundant constituents of the lighter sands from 

 Snake River localities. It occurs as thin chips of a smoky gray to 

 black color which have sharp edges and show traces of conchoidal 

 fracture. The cliips are not at all water-worn. 



GOLD. 



Gold in grains, flakes, and nuggets occurs frequently in the sands, 

 and in many of those which contained no visible gold it was prob- 

 ably originally present having been removed by amalgamation. Flat 



