398 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



on the authority of Krantz as occurring in the Idria mine. Since that time 

 Lipoid has written two careful memoirs on tlie Idria deposit, but he does not 

 refer to these pseudomorphs. On the contrary, he states that in tlie dolomite 

 rock cinnabar occurs for the most part as mere paints or thin incrustations 

 (zarte Anfliige), and mentions dolomite crystals and cinnabar as of simulta- 

 neous deposition from the ore-bearing- solutions. In view of these facts and 

 considering that dolomite and cinnabar each show a considerable variety of 

 faces of the rhombohedral system, to which both belong, it appears to me 

 nearly certain that Krantz was in error and that cinnabar has not been 

 observed replacing dolomite. 



The. substitution of a metallic sulphide for a sulphate or a carbonate 

 of an alkaline earth seems strange, but there is no reason to doubt that such 

 tran.sformations occur. While it is extrenielj' doubtful whether cinnabar 

 has ever been found as pseudomorphs after non-metallic, inorganic minei'als, 

 there is good evidence that galena has replaced calcite, and probably also 

 dolomite. Sillem found pseudomorphs after calcite at Andreasberg and at 

 Pribram' and A. E. Reuss found at Rodnau, in Transylvania, transforma- 

 tions of calcite into a mixture of galena and pyrite." Such replacements have 

 also attracted attention in this country. In 1880 I suggested that there was 

 evidence tending to prove that the lead ores of Eureka, which are galena 

 and its derivatives, had replaced the more or less dolomitic limestone in which 

 the deposits are inclosed.' Later Mr. J. S. Curtis made more observations 

 on the same deposits, which seemed conclusive of this substitution,* and Mr. 

 S. F. Eunnons has shown that the same conclusion is to be drawn with 

 reference to the lead deposits in limestone at Leadville.^ In case of a real 

 replacement the rock replaced will be represented in the resulting ore bodies 

 only by residual kernels, and where action has been vigorous few such 

 kernels will remain. Both Mr. Curtis and Mr. Eumions call attention to 

 the rarit}- of calcium carbonate in the lead ores of the respective districts 



'Neues Jahrbuch fiir Mineral., 1851, p. 397. Sillem's observations were not called iu question by 

 Reuss, as sfenis to bave been supposed (Allg. Geol., Kotb, vol. 1, p. 172), for, tbougli tbe latter did 

 not observe this cbange at Pribram, in speaking of the Rodnau occnrreuce be mentions tbe replace- 

 ment as " already proved elsewhere," and he can have referred only to Sillem's observations. 



^Sitzungsber. k. Akad. Wiss., Wien, vol. iO, 1853, p. 67. 



3 First Ann. Kept. U. .S. Geol. Survey, 1880, p. 38. 



■•Silver-Lead Deposits of Eureka, Nevada, Mon. U. S. Geol. Survey No. 7, 1884, p. 104. 



* Geology and Miniiig Industry of Leadville, Colorado, SIou. U. S. Geol. Survey No, 12, 1886, 

 passim. 



