THE MINERALS OF IDAHO 479 



from 3 feet to 5 feet in thickness. The upper bed varies from 14 

 inches to 9 leet in thickness but is very dirty and impure. The 

 material is of no great value as fuel because of its high ash and 

 moisture content. A typical analysis is given below: 94 



Analysis of lignite coal, W orthington mine, Goose Creek district 



Per cent 



Moisture 11. 30 



Volatile matter 35. 80 



Fixed carbon 28. 50 



Ash 24. 40 



Sulphur .85 



Total 100.85 



Calories 4,370 



British thermal units 7, 860 



CLEARWATER COUNTY 



In the Orofino field around Orofino in Clearwater County, and 

 extending into Lewis and Idaho Counties, coal ranging from lignite 

 to subbituminous occurs in beds 3 feet or less in thickness between 

 beds of clay and sandstone which are interstratified with the Columbia 

 River basalt flows. The coal is jet-black and is mostly dull, but 

 has a few bright layers. Woody structure is evident in parts of the 

 coal and as a whole it is laminated, showing thin plates ranging 

 from films to bands 3 mm. in thickness. The fracture is irregular 

 and the jointing somewhat columnar. Considerable resin in globules 

 as much as 8 mm. in diameter occurs along the bedding planes of 

 the coal. The coal is hard and when pulverized gives a black powder 

 with a brownish tint. 95 



FREMONT COUNTY 



In Fremont County the Horseshoe Creek coal bearing district is a 

 division of the Teton Basin coal field. The Horseshoe Creek district 

 is 25 miles southeast of St. Anthony and 10 miles southwest of 

 Haden station on the Oregon Short Line Railroad. The district 

 covers 6 square miles, only a part of which is underlain by coal beds 

 which are thick enough to be workable. The beds of coal are not 

 continuous and vary greatly in thickness. The thickest bed ex- 

 posed is at the Horseshoe mine. Here the coal is 11 feet thick, but 

 it includes a 10-inch bed of sandstone and almost 2 feet of bony 

 coal. At the Brown Bear mine the coal averages 5 feet in thickness, 

 but includes some small shale partings. The coal-bearing strata 

 dip steeply and the area is much faulted. The coal is black and hard 

 but it is badly shattered and broken by faulting in the area. Much 



»« C. F. Bowen. U. S. Oeol. Survey, Bull. 531, p. 252, 1913. 

 s» C. T. Lupton. U. S. Oeol. Survey, Bull. 621, p. 99, 1915. 



