gg UNIVERSITY OF MISSOURI STUDIES 



hot, altho the temperature would probably be less than 200° C, 

 since deposition took place near the surface. 



Most of the ore deposits of the western United States that 

 were deposited at intermediate and shallow depths contain barite 

 as one of the gangue minerals. This is true of mineral veins of 

 this type all over the world. In many instances it is so abundant 

 as to give rise to solid veins of barite, as at Aspen, Colorado, and 

 the baritic veins in the Freiberg district in Germany. These 

 baritic veins may become so rich that they are worked for barite 

 alone, as, for example, in the Erzgebirge in Saxony. In other 

 cases it is a very common gangue mineral. These facts show 

 that barite is a mineral of deep-seated origin in a great many in- 

 stances. This fact is of even greater significance for it proves 

 that the sulfate radical exists in hot solutions. 



Not only is barite found as a gangue mineral in mineral de- 

 posits at various depths, but it it found as a constituent of 

 several hot spring deposits. Furthermore, it is associated with 

 radio-active substances in some of these hot spring deposits. 

 This last fact is of note in connection with Boltwood's^ sugges- 

 tion that barium may be derived from actinium as an end product. 



The discussion of the deposition of the barite by rising hot 

 solutions includes a study of the mode of occurrence of the de- 

 posits, the mode of egress of the solutions, the source of the 

 solutions, and the time of mineralization, with the presentation 

 of corroborative evidence. 



Mode of occurrence of the deposits 



The description of the barite deposits above has presented 

 the features in full, but they can be reviewed here as it is essential 

 to keep the facts of occurrence in mind. 



The barite is found in veins, as replacement stringers at- 

 tached to the veins, as disseminated deposits which are in part 

 filling and in part replacements, as cave deposits which are pri- 

 marily filling, and as residual deposits. The residual deposits 

 do not need to be considered here, except in so far as retained 

 features from the original deposits are evidence of previous con- 

 ditions. 



•Boltwood, B. B., Amer. Jour. Sci., vol. 20, p. 257. 1905. 



