THE MINERALS OF IDAHO 409 



red almandite in sharp trapezohedral crystals, the remaining 50 per 

 cent being largely samarskite and columbite. The columbite is 

 relatively more abundant than in the first sample examined. The 

 samarskite is entirely like that already described, showing rounded 

 pitted grains and rough crystals. Some of these have grains of 

 quartz and crystals of muscovite attached to them, while others seem 

 to show either two minerals or two generations of samarskite, some 

 of the grains, where broken, showing an inner crystal surrounded by 

 an outer shell of a similar substance. The sample labeled " chromite ' ' 

 contains a little samarskite but is, for the most part, composed of 

 ilmenite. 



HIELMITE (531) 



Stanno-columbate and tantalate of Orthorhombic. 



yttrium, iron, manganese, calcium, 

 etc. Formula doubtful. 



CLEARWATER COUNTY 



Out of a concentrate from a placer mine at Pierce, Clearwater 

 County, labeled "Rutile and aeschynite," there was selected a small 

 waterworn pebble, less than a centimeter in diameter, which was 

 very tough when broken and had conchoidal fracture and very 

 brilliant submetallic to resinous luster. Under the microscope the 

 material of this small mass was doubly refracting with a mean index 

 of refraction between 2.31 and 2.40. The birefringence was 0.02, 

 color very dark brown; pleochroic. Hardness 4.5, specific gravity 

 6.18; streak red-brown. These properties are nearer those of 

 hielmite than any other of the rare earth minerals. The mass was 

 lost without any chemical tests having been made. 



AESCHYNITE (532) 



Chiefly a columbate and titanate of the Orthorhombic. 



cerium metals. 



CLEARWATER COUNTY 



A lot of waterworn grains and small black pebbles received by 

 the National Museum from Pierce in Clearwater County is labeled 

 "Rutile and aeschynite." Presumably aeschynite has been identi- 

 fied in this material by someone, although most of the pebbles 

 examined by the writer proved to be rutile of unusual colors. One 

 piece was tentatively identified as hielmite and a crystal was meas- 

 ured which could not be identified. Aeschynite may occur, since 

 only a small proportion of the masses, all of which look alike, could 

 be examined. 



54347— 26t 27 



