BLUE LIMESTONE. 



65 



The following complete analyses of typical specimens, taken from local- 

 ities at considerable distances from each other in the vicinity of Leadville, 

 are further proofs of the uniformity of composition. I, II, and III are 

 from the upper of the Blue Limestone, IV from near its base, and V from 

 the upper part of the White Limestone. 



The coloring matter is in part evidently organic, but iu part, as sug- 

 gested by Mr. Guyard, may be due to the presence of salts of iron. He 

 says that he finds an appreciable amount of sulphide of this metal which will 

 produce a black color. A remarkable feature in this analysis, as well as 

 in that of the White Limestone, is the presence of appreciable quantities 

 of alkaline chlorides. Microscopical examination under very high power 

 (1,136 diameters) shows that the dusty appearance is due to minute specks 

 in the grains composing the rock, which are fluid inclusions, in some of which 

 the rapid movement of a bubble is visible. As will be shown later, it seems 

 fair to assume that the included liquid consists of alkaline chloride. The 

 microscope also shows that the rock is very finely granular, the size of 

 the grains varying from .05 to .10 of a millimeter in diameter. No twin 

 crystals of calcite are observed, and very little quartz or ore particles could 

 be detected. 



MON XII 5 



