210 Hidden and Hillebrand — Description of Rowlandite. 



II. Analysis and Discussion of composition, by W. F. Hillebrand. 



The specimen of rowlandite, furnished by Mr. Hidden for 

 analysis, was a portion of a mass resembling somewhat amorph- 

 ous gadolinite. It had a glassy interior surrounded by an un- 

 even thickness of reddish alteration substance, chiefly a carbo- 

 nate, or carbonates, of the rare earths and lime. The glassy 

 " rowlandite " showed, when broken up, reddish and dark 

 stains in places, the latter being produced by minute black 

 inclusions, perhaps of a titanium mineral. Numerous scarcely 

 visible fissures, filled with foreign matter, traversed the glass. 

 This rendered the selection of pure material an arduous task ; 

 the result of several days of labor, however, was a sample 

 possessing a high degree of purity as shown by the micro- 

 scope. A very small amount of impurity was still present, but 

 much less, apparently, than the analysis seems to indicate. A 

 slight cloudiness in some grains points to incipient change. Its 

 density is the same as that found by Mr. Hidden, 4*513, at 

 15*5° C. The analysis is as follows : 









Mean. 



Si0 2 .__ 



25-77 



26-04 



26-04* 



Xf 



•39 





•39 



ThO a 



•59 





•59 



Ce 2 3 t 



5'06 





5-06 



La group 



9-34 





9-34 Mol. Wt. 336'8 



Yt group 



47-70 





47-70 Mol. Wt. 266-2 



Fe 2 3 



•09 





•09 



FeO 



4-39§ 





439 



MnO 



-70 



•64 



•67 



CaO .._ 



•60 



•40 



•50 



MgO 



1-58 



1-66 



1-62 



Alk ..__ 



•32 



•24 



•28 



H 2 .. 



•24 



•34 





•24 



co 2 .___ 



•34 



Fl 



3-87 





3-87 



PA 



trace 





trace 





101-12 





Less O for Fl, 



1-63 



99-49 



* Certainly more nearly correct than 25*71, since the fluorine must have caused 

 loss of silica on evaporation with hydrochloric acid. 



f A mixture of undefinable earths with some uranium and a trace of titanium. 



\ Cerium dioxide cannot be present, if at all, in more than trivial amount, for 

 otherwise much less ferrous oxide would have been found. For the same reason 

 the manganese cannot be present as Mn 2 O s . 



§ If the small and undetermined amount of uranium exists as dioxide, the fer- 

 rous oxide here given is correspondingly high, but the possible error can have no 

 influence on the formula deduced. 



