204 Bulletin of Laboratoucs of Demsoii University. [Voi.xii 



Litholo.^ically, the formation is not entirely uniform, but in 

 places it shows considerable variation, both in composition and 

 texture, and in color as well. It is composed principally of a 

 compact, fine-G^rained vitreous quartzite varying from light to 

 dark gray in color, and in places containing beds of fine-grained 

 conglomerate. Intercalated beds of a drab to darker colored 

 siliceous shales of varying thickness, much crumpled, contorted 

 and altered in places, are often met with. The formation con- 

 tains much pyrite in the form of grains and crystals in places, 

 and this mineral seems to be equally abundant in both the quart- 

 zite proper and the interbedded shale layers. The two min- 

 eralogically-unlike beds, shale and quartzite, are likewise ocher- 

 bearing, and the difference in composition of the rock serves as 

 a basis for making two grades of the ocher. The o( her found 

 replacing the shales is prevailingly darker in color, because of 

 the large proportion of admixed argillaceous or clayey matter 

 derived from the shales, which cannot be separated from the 

 refined ocher ; while the ocher found replacing the quartzite 

 proper is uniformly lighter in color, because of less admixed 

 clay. 



The effects of intense pressure-metamorphism are plainly 

 evident in all parts of the quartzite formation, as shown in Fig, 

 3. As a result of the action of the compressive forces the 

 quartzite layers have been sharply folded, and in addition the 

 formation has been extensively crushed and shattered over 

 most of its parts, especially in the ocher-bearing portions. So 

 extensively crushed and shattered is the quartzite as indicated 

 in some of the sections of the larger ocher-openings in the 

 area, that it is almost impossible to determine the original bed- 

 ding of the rocks. As often shown by its brecciated condition, 

 the qua''tzite is presumably cut by numerous faults, but such 

 lines of fracture, if they exist, have not been traced. As 

 Hayes has stated, the physical forces were probably attended 

 by increased chemical action, inferred from the formation of 

 the ocher. 



The composition of the quartzite proper is shown in the 

 chemical analysis below made by the N. P. Pratt laborator)-, in 



