41 



Parisite from Muso. Mineral from Narsarsuk. 



Composition: Ce^F^CaC.^O^ CeFCaC^O^ 



Cleavage: Distinct basal No distinct true cleavage 



Sp. Gr.: 4,364 3,902 



Refractive indices: со = 1,569 1,6742 



s = 1,670 1,7701 



Crystallization: Hexagonal Trigonal 



These differences are so important that, if all the state- 

 ments could be accepted as correct, the mineral from Narsar- 

 suk which I have here described , and the parisite from Muso 

 should be regarded as two distinct mineral species. The correct- 

 ness of the statements as to the Muso mineral is, however, 

 in my opinion not quite beyond all doubt. The chemical for- 

 mula of the mineral cannot be definitely established, as long as 

 the analyses shows a considerable loss. If this loss represents 

 fluorine, the formula of Damour and Deville will hold good. If, 

 on the other hand, the loss consists, for instance, of lime, the 

 composition approaches somewhat more to that of the mineral 

 from Narsarsuk. But in this case no simple relation between 

 the amounts of calcium carbonate and fluorcarbonate of the rare 

 earths is obtained ; that these substances should replace each other 

 isomorphously, can hardly be assumed M. The discrepancy as 

 to specific gravity may to some extent be explained as due 

 to the fact of the Muso mineral containing a considerably 

 larger amount of the beavv earths than does the other mineral. 



') After the above was written , an article on parisite from Ravalli Co., 

 Montana, has been published by S. L. Penfiel d and C. H. Warren 

 (Amer. Journ. of Science, 1899, 4 Ser., Vol.8, p. 21). In this article an 

 analysis made by Warren on parisite from Muso is also given. This 

 analysis agrees very closely with the formula Ce.^F.^CaC^O^ given above. 

 This composition also belongs to the recently discovered parisite from 

 Ravalli Co., which has, likewise, been found to be holohedral hexagonal. 

 These facts are of the greatest importance with regard to the position of 

 the mineral from Narsarsuk 1 hope soon to come back to the question. 



