BAIN.] 



ORIGINAL SOURCE OF ORE MATERIAL. 



65 



Mr. Smith's analyses, made by Mr. George Steiger, of the United 

 States Geological Survey, are quoted below. 



Analyses of limestone from Kentucky and Missouri. 



MgO 



CaO 



F 



BaO 



Organic matter Trace 



II. 



III. 



IV. 



"Doubtful trace. 



I. Ste. Genevieve limestone from near View. Ky. 

 II. Ste. Genevieve limestone from near Crider. Ky. 

 III. St. Lonis limestone from Crittenden Connty. Ky. 

 IV. Limestone from Shoal Creek, southeast of .Joplin, ]Mo. 



While there is always doubt attacliing to the origin of these minute 

 quantities of material, and it is impossible to make sure that they do 

 not represent secondarily-introduced material, it would seem that the 

 limestone is at least a possible competent source of the fluorite. 



As a constituent of igneous rocks liuorite is common. It enters into 

 the composition of a number of widelj" disseminated minerals, includ- 

 ing the common variety of apatite, certain micas, and topaz. Of these 

 the first two named occur in unusual abundance in the dike rocks of 

 this vicinity, though it is not certain that the particular minerals 

 found here are fluorine bearing. Analyses of the freshest dike rock 

 available, made in the Geological Survey laboratory by Mr. George 

 Steiger, gave the following results : 



Fluorine in analyses of dike rock of southern Illinois and Kentucky. 



Per cent. 



Downey dike, Rosiolare, 111 None. 



Mix dike. Golconda, 111 0.13 



Hard dike, Marion, Ky None. 



It is of interest to recall in this connection the fact that in even the 

 most altered of the igneous rocks the apatite, presumably the mineral 

 carrying the largest amount of fluorine, is fresh and unaltered. 



Fluorine has commonly been observed in connection with volcanic 

 outbursts, and fluorite is one of the most common minerals connected 

 with volcanic rocks. At Cripple Creek. Colorado, and many other 

 western camps it is abundant in intrusive and extrusive rocks of Ter- 

 tiarj^ age. 



So far, then, the igneous rocks form a very probable source of the 

 Bull. 255—05 M 5 



