548 W. T. Schaller — Composition of Hulsite and Paigeite. 



In the ratios of the above analysis, the CaO, Si0 2 and A1 2 3 

 are excluded as belonging with the insoluble matter to the 

 gangue. As obtained from the average analysis, they are : — 



Eatios of analysis of sample No. 3, paigeite. 



FeO. _ -486) 



MgO -056 \ 285 



Fe 2 3 -093 4-9 



Sn0 2 -019 1-0 



B 2 3 ._ -099 5-2 



H 2 .... 



Like one of the hulsite analyses, the calcium oxide is con- 

 siderably higher in sample No. 3 than in sample No. 2 and it 

 seems as if some of the lime belonged to the borate. It would 

 need only 1*57 per cent, of CaO to raise the ratio of 

 (FeO+MgO + CaO) to Sn0 2 from 28*5 : 1, as given above, to 

 30 : 1. This small amount of lime may, therefore, be con- 

 sidered as belonging to the borate. The ratios then obtained 

 are 28'5 or 30-() l KO.4-9Fe 2 O 3 .lSnO 2 .5-2B 2 O 3 + ? H 2 0. 



Discussion of Formulae of Paigeite. 



From the above three series of analyses, the following are 

 the formulae deduced for paigeite : 



Formulae for Paigeite. 



EO Fe 2 3 Sn0 2 B 2 3 H 2 



From sample No. 1 31*1 5*0 .__ 6*7 5*4 



2 .. 29-4 5-6 



3 



\ 



28-5 4-9 1-0 5-2 ...or 



30-0 4-9 1-0 5-2 



The average of the above shows that the most probable 

 formula for paigeite and the one proposed for the mineral is : 

 30FeO.5Fe 2 O 3 .lSnO 2 .6B 2 O 3 .5H 2 O. While the above formula 

 is complex and yields a rather high ratio of FeO to Sn0 2 , there 

 does not seem to be any other interpretation to the analyses. 

 While not impossible that paigeite is a mixture of two or more 

 closely related minerals, nothing but the unusual composition 

 indicates such a mixture. The constant small percentage of 

 tin oxide shows that the mineral is essentially different in 

 ratios from the corresponding hulsite. The occurrence in 

 wavy lamellar masses of line radiating libers, the intense shiny 

 black color, the marked tendency as seen in thin sections for 

 the individual fibers and masses to fray out at the ends into a 



