130 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



what higher horizon than the ore body. This porphyry resembles the rock 

 of the lower intrusive sheet shown in the sketch, and may form part of it, 

 though it was not possible to trace the connection between the two. 



Loveiand Hill Loveland Hill affords an excellent illustration of the often- 

 observed fact that the deeper transverse valleys often follow the line of a 

 minor or lateral anticlinal fold, while the intermediate hills or more ele- 

 vated region, which has been relatively less eroded, is the locus of a minor 

 synclinal fold. 



On the broad, flat back of this hill or spur, whose slope corresponds 

 very nearly with the easterly dip of the sedimentary beds, is a shallow 

 ravine draining into Mosquito gulch, towards which there is a very per- 

 ceptible dip of the beds from either side; in other words, the strata dip 

 eastward, and at the same time dip north and so'ith towards the bottom of 

 this valley. The larger part of the surface of the hill is covered by beds 

 of Blue Limestone The White Limestone comes to the surface at its upper 

 end, and on the sharp ridge which separates the north Mosquito amphi- 

 theater from Buckskin gulch are the remains of the lowest quartzite beds 

 of the Cambrian. The Blue Limestone has been extensively prospected for 

 ore, and a number of irregular deposits have been discovered, generally 

 occupying gash veins, or cross joints and fault planes in the limestone. 

 Numerous irregular bodies of porphyry are also found. Time did not 

 admit, however, of a complete study of these beds nor of the ore deposits. 

 The principal facts ascertained will be found in the description of mines in 

 Part II, Chapter V. 



The synclinal ravine already mentioned divides the hill somewhat un- 

 equally into a northern and a southern portion. The former forms a con- 

 tinuous ridge, which extends down to the junction of Mosquito Creek with 

 the Platte River below Alma. East of the mouths of the canons this ridge 

 is comparatively low and covered with forests and soil. It is made up of 

 beds of the Weber Grits formation, in which there is evidence of a sec- 

 ondary roll, as shown in Section C, Atlas Sheet VIII. Along the steeper 

 slopes of the spur between Buckskin Joe and Park City are outcrops of a 

 body of quartz-porphyry of the Lincoln type, which apparently forms a 

 sheet above the Blue Limestone. These outcrops are not very continuous, 



