528 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



these joints is, as at the Criterion mine, generally northeast and southwest. 

 Their plane is practically at right angles to the stratification. A slight dis- 

 cordance is frequently observed in the beds on either side of the plane, 

 showing a displacement of a few feet. Among those noticed is the Ernest, 

 at the foot of the cliffs just back of the Phillips mine. Here may be seen 

 a phenomenon not uncommon in unstratified rocks, the crumpling of a certain 

 bed, which does not extend to the adjoining beds. This may be supposed to 

 be the result of unequal plasticity, by which, as an effect of lateral com- 

 pression, one bed has been crumpled or folded, when the others, being 

 more plastic, have expanded sufficiently to allow for the longitudinal con- 

 traction. The Ernest is in the upper part of the White Limestone, as is 

 the Rock Island, a little higher up the canon. The Northern Light, which 

 is shown in Plate XIII, is in the Lower Quartzite, and has a gangue of 

 calc spar. Its vein material has a maximum thickness of 6 feet. Still to 

 the west of this is the Rock Island, which is in the upper part of the White 

 Limestone. 



LOVELAND HILL. 



In the Blue Limestone, which covers the surface of Loveland Hill, 

 are a great number of prospect holes and small mines, which have opened 

 irregular bodies of ore, principally argentiferous galena and its decompo- 

 sition products. 



Fanny Barrett mine (L). The most important of these is the Fanny Barrett, 

 which is situated not far from the edge of the cliff overlooking Buckskin 

 gulch, and apparently near the line of fault noticed on the .south wall of Buck- 

 skin gulch. It is about on the line of strike of the Criterion deposit. The 

 ore fills a so-called fissure some four feet in width, containing galena and what 

 is called by the miners "hard carbonate," i. e., a sulphate of lead, forming 

 greenish- white concentric layers like agate, with some carbonate of copper. 

 The gangue is a soft hydrated oxide of iron, with considerable oxide of 

 manganese, which gives it a black color. In places the ore forms branch- 

 ing deposits and lenticular bodies of considerable size along the stratifica- 

 tion planes. The fissure is supposed to have been traced quite across the 

 crest of Loveland Hill to the cliffs facing Mosquito and Buckskin gulches 

 on either side. On the Buckskin side, a little above the contact of the 

 Archean with the Lower Quartzite, a body of ore has been opened in the 



