Prosopite, Jefersonite, Oovellite, etc. 53 



Neglecting the three last constituents in each case, the ratios 

 become for 



Bastnasite R : F, C0 3 = 1 : 2*94 



Tysonite R : F, C0 3 = 1 : 3-05 



which ratio for tysonite is not changed by allowing for admixed 

 bastnasite. 



The above direct fluorine determinations fully establish the 

 hitherto assumed formulas, R /,/ F 3 / for tysonite and R'^F/CO,") 

 for bastnasite. 



Pro sopite. 



Over two years ago Mr. Geo. F. Kunz sent for examination 

 a beautiful pale green mineral from Utah, supposed to be iden- 

 tical with the green variscite called by him utahlite in Mineral 

 Resources of the IT. S., 1894, p. 602. Under a recent date 

 Mr. Kunz writes that Mr. T. H. Beck of Provo found the 

 mineral " in 1895, in the Dugway mining district, Torvel Co. 

 It was found in a low range of hills about five miles long, sur- 

 rounded by a desert on an arid region occurring as flat rock, 

 associated with fluorite, native silver and slate, and trachytic 

 rock (?), containing decomposed pyrite in which there was 

 present a little free gold." 



Unexpectedly this was found to be the hydrous aluminum- 

 calcium fluoride prosopite, mixed with some quartz and proba- 

 bly fluorite and colored by a small amount of some copper salt. 

 A new and interesting occurrence for this very rare mineral is 

 thus afforded. 



The material as prepared for analysis after separation by a 

 heavy solution proved to be still far from pure ; quartz grains 

 in amount from one to two per cent were left undissolved after 

 complete conversion of the fluorides into sulphates and pre- 

 sumably considerably more had been removed by the escaping 

 fluorine. The total amount of quartz was not determined and 

 the material at hand did not suffice for attempts at more com- 

 plete purification, so that the conclusions drawn from the 

 analysis, while extremely probable, are not to be taken as alto- 

 gether proven. 



The sp. gr. of the mineral as analyzed was 2*87 at 21° C. and 

 the hardness about 4*5, both agreeing with the constants for 

 prosopite. Furthermore, but little of the water (1*25 per cent) 

 was expelled by several hours heating at 280° C. Analysis 

 gave : 



