GEOLOGY EOCKS EAST OF FEOXT RANGE LIGNITIC, 127 



Js'o. : Nature of strata. 



Thickness, 

 iu feet. 



Top, (northeast.) 



Coal, No. .5 



Sandstone and clay 



Coal, No. 4 



Sandstones 



Fire-clay 



Coal, No. 3 



Sandstones 



Fire-clay 



Coal, No. 2 



Fire-elav 



Coal, No. 1 



Shale and sandstone 



5 



16 



1 



6i 

 3 

 3 



64 

 4 

 2 

 5 

 3 

 5 



Coal No. 5 is mined by a shaft 15 feet in perpendicular depth at the 

 end of the drift. 



"Wheeler mine ; range 70 west, township 4 south, section 14. The bed 

 has a course of south 45° east, magnetic, and dip of 74P ; is 7 feet thick, 

 and has been worked to a depth of 40 feet, furnishing coal not of very 

 good quality. 



Eowe mine ; range 70 west, township 4 south, section 23. The course 

 of the bed is here south 48° east, and dip nearly vertical where mined, 

 though it is 70° east near by. The coal is 4 to 6 feet thick, and is the 

 lowest of several coal-beds near by. Dr. Hayden gives the following 

 section : Top, arenaceous clay, 3 J feet ; coal, 4 feet ; clay, 3J feet ; coal, 4 

 feet ; clay, 5 feet, base. The coal is reached by -passing 141. feet through 

 sandstone. Its ash is white, like pine-wood ashes, and small in quantity. 

 Up to 1868, 250 tons of coal had been taken out, but in 1872 the mine 

 was idle for want of good communication. 



Mann opening ; range 70 west, township 4 south, section 24. 



Wilson mine; range 69 west., township 4 south, sections' 31 and 32; 

 •course, south 50° east, magnetic ; not mined now. 



Gilpin (or Wenrich) mine; range 69 west, township 5 south, section 9. 



Jones mine ; range 69 west, township 5 south, section 35. 



A little farther south coal was opened near the Platte in 1806. It 

 occurred in two beds, in all about 5 feet thick, separated by about 2 

 feet of clay, and not of very good quality. On the opposite (south) side 

 of the Platte, in the continuation of the same line of outcrops, coal has 

 also been opened, and a considerable quantity used in Denver. 



Iron. — Iron concretions occur here and there scattered through the 

 clays and shales of the lignitic formation at certain points, usually in 

 the coal horizons, and may be so continuous as to give the idea of a per- 

 manent bed. By the weathering away of the inclosing rock, as the 

 degTadation of the surface by erosion goes on, these concretions some- 

 times accumulate in sufficient quantities to appear as solid ledges of ore. 

 In the South Boulder Valley these accumulations cover quite large areas. 

 The.se nodular masses are of limonite, more commonly known as brown 

 hematite, or brown iron-ore, and probably originally existed in the beds 

 iu which they occurred as clay, iron, stone. They vary from an ounce 

 to a ton or more in weight, and on breaking them open they are often 

 found to have a regular concentric structure, like the layers of an agate, 

 the layers perhaps varying in color from brown to yellow, while many 

 of the nodules are full of impressions of leaves in Ixagments, stems, 

 grasses, &c. From the vicinity of the Marshall mines, on South I3oulder 



