ransome: wurtzite at goldfield 485 



That sphalerite, under natural condition, may change by mo- 

 lecular rearrangement into wurtzite was suggested by Laspeyres^ 

 and more definitely stated by Noetling,^ who concluded as the 

 result of his investigation that sphalerite is primary and wurtzite 

 secondary in origin.^ 



The conclusion that when sphalerite and wurtzite are asso- 

 ciated, the wurtzite is generally of secondary origin appears to 

 have considerable support from direct observations; but this 

 relation, if it is true, still lacks satisfactory explanation. If, for 

 example, the wurtzite has been deposited by descending acid 

 solutions, it is not clear why it should be so intimately asso- 

 ciated with or replace the less soluble sphalerite. On the other 

 hand if sphalerite, theoretically the more stable mineral at ordi- 

 nary temperatures, undergoes change to wurtzite, the cause of 

 this change is equally obscure. Although it is well known that 

 sphalerite may be changed to wurtzite by heating to about 

 1100°C.,^ this is probably not a common natural mode of for- 

 mation of the latter mineral. Whether the change of sphalerite 

 into wurtzite can be effected by treatment with acid solutions 

 at moderate temperatures has not been determined so far as I 

 am aware, but this question appears to be easily within the 

 range of experiment. 



The rather inconclusive evidence as to the paragenetic rela- 

 tionship of the two zinc sulphides at Goldfield leaves the mode of 

 origin of the wurtzite in doubt. The suggestion is favored that 

 the wurtzite is later than the sphalerite and represents a mo- 

 lecular rearrangement of that mineral. But the explanation 

 originally offered for the deposition of the ores through a mingling 

 of alkaline and acid solutions is quite in harmony with the suppo- 

 sition that the sphalerite and wurtzite crj^stallized at approxi- 

 mately the same time. 



^Laspeyres, H., Mineralogische Bemerkungen, Zeits. f. Krist., 9: 191. 1884. 



^ Noelting, J., Ueber das Verhaltniss der sogenannten Schalenblende zur regu- 

 laren Blende und zum hexagonalen Wurtzit. Inaug. Diss., Kiel, p. 28. 1887. 



* " Jedenfalls beweisen die Untersuchungen der Blenden von StoUberg, Schar- 

 ley, Bleischarley, Altenberg, Wiesloch und Miechowitz, dass die Blende primaren 

 und der Wurtzit secundiiren Ursprungs sein muss" (p. 29). 



" Allen, Crenshaw and Merwin, op. cit., p. 344. 



