478 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



LEMHI COUNTY 



An old specimen (Cat. No. 56532, U. S. N. M.) labeled as from 

 the Lena Delta mine, Lemhi County, contains a few pale yellow tabu- 

 lar wulf enite crystals in ocherous limonite. The crystals are bounded 

 by e(011), o(012), p(lll), and 6(113) (fig. 168). 



MINERAL COAL 



Despite its practical value and importance coal is of little value 

 or interest to the mineralogist and can scarcely be properly regarded 

 as a mineral. The following abstracts merely include references 

 to the most noteworthy occurrences of coal in Idaho. 



BOISE COUNTY 



Subbituminous or lignite coal occurs in Boise County at Horseshoe 

 Bend and Jerusalem Valley on Payette River, 20 miles north of 

 Boise and 40 miles southeast of Weiser. The field occupied by the 

 coal-bearing formation is about 15 miles long in a northeast-south- 

 west direction with an area of about 23 square miles. The beds of 

 coal, which are mostly less than 14 inches thick, occur interstratified 

 with unconsolidated sands and clays belonging to the Payette for- 

 mation which is of Eocene age. The coal has a pitch-black color, 

 vitreous luster, black streak, bedded structure, a tendency to pris- 

 matic cleavage, an irregular to subconchoidal fracture and a denser 

 texture. A typical analysis is as follows: 93 



Analysis of coal from Henry mine, Horseshoe Bend 



Per cent 



Moisture 5- 00 



Volatile matter 40. 40 



Fixed carbon 38. 10 



Ash 16.50 



Sulphur • 54 



Total 100. 54 



Calories 6, 130 



British thermal units 11, 030 



CASSIA COUNTY 



In Cassia County the Goose Creek coal-bearing district has an 

 area of 156 square miles. Here lignite occurs in beds in sediments 

 which are presumably ol Eocene age and which greatly resemble the 

 Payette formation. The lignite, which when fresh is black or very 

 dark brown, weathers to flakes and scales, which show the presence 

 of a considerable amount of earthy matter. There are two main 

 lignitic coal beds, the lower of which is the best in quality and ranges 



m C. F. Bowen. U. S. Geol. Survey, Bull. 531, p. 245, 1913. 



