ART. 3. BLACK SANDS FROM IDAHO SHAjSTNON. 29 



flakes of gold are of frequent occurrence in sands from Rosa, Bing- 

 ham County, and less abundantly so in other Snake River sands 

 from Wapi and Minidoka. Small rounded grains of a deep yellow 

 color were noted in the nonmagnetic residue of a sand from Bear 

 Creek, in Camas County. An " oversize " sample of coarse material 

 from Centerville, consisting of pebbles of garnet, granular magne- 

 tite, irregular ilmenite, and several radioactive uranium minerals 

 contained several slightly worn rusty quartz pebbles containing abun- 

 dant pale-colored gold. 



CYANITE. 



While not properly a mineral of the heavy sands, cyanite was seen 

 as grayish-blue blades in a rusty granular quartz matrix in one 

 pebble from an unscreened sand from Snake River at Minidoka. 



EPIDOTE. 



Epidote may occur sparingly in some of the sands examined, being 

 similar in appearance to augite and olivine, from which it could not 

 be distinguished by its appearance alone. Pebbles of pale-green epi- 

 dote in massive granular form were noted in the coarser portion of 

 sand from Rosa, Bingham County, associated with pebbles of sim- 

 ilarly fine-grained brown garnet, both evidently being fragments of 

 a metamorphic hornfels. 



CINNABAR. 



Cinnabar occurs sparingly in a sand from Pierce City, which con- 

 sists largely of ilmenite in brilliant black grains and also contains 

 rutile, monazite, and zircon. The cinnabar is deep red in color with 

 a grayish metallic cast. The majority of the grains are rounded 

 pebbles of fine granular, massive cinnabar, but many of them are 

 more or less transparent fragments of single cinnabar crystals and a 

 few are crystals bounded by imperfect faces which could not be 

 identified. It seems probable that much of the cinnabar of the orig- 

 inal gravel was in larger masses which were eliminated by screening. 



The United States National Museum collections contain pebbles of 

 impure massive cinnabar up to 1 inch in diameter from a placer near 

 Resort. Small rounded grains of cinnabar were noted in small 

 number in the polycrase-bearing sand from Centerville. 



LIST OF LOCALITIES AND COMPOSITIONS OF HEAVY SANDS EX- 

 AMINED. 



The following list gives the locality', average size of grain, and. 

 chief minerals of the 52 sands from Idaho localities which were ex- 

 amined during the course of the present work. Each sand is as- 



31.S6— 22— I'roc.N.M.Vol.CO 7 



