Penfield and Sperry — Mineralogical Notes. 323 



though owing to its very high atomic weight it is represented 

 "by a much greater percentage in the analysis. The identity of 

 the thoria was proved by making an atomic weight determina- 

 tion on -0276 grams of the oxide and by converting it into sul- 

 phate which gave 228 instead of 232, an agreement as close as 

 could be expected from the small quantities used. The joint 

 molecular weight of the (Ce, La, Di) 2 3 was found to be 328. 

 The amount of Th0 3 is here too small to warrant any general- 

 izations as to whether it is present as a silicate, which is cer- 

 tainly substantiated by our analysis, or whether it belongs to 

 the phosphate. Regarding the ThO a and Si0 2 as present in 

 the form of thorite, the P 2 5 and (Ce, La, Di) 2 3 are present in 

 the proportion of a normal phosphate, as shown by the ratio, 

 •207 : '210=1 : 1. Th0 2 can not be regarded as an essential 

 constituent of monazite, as it is present in varying proportions, 

 though almost always present in the different varieties. 



4. Sussexite from Mine Hill, Franklin, JV. J. 



This rare mineral was first described by Professor Geo. J. 

 Brush,* who determined its formula to be HRB0 3 , where R= 

 Mn and Mg. A new analysis of this mineral was to be desired, 

 especially for the more accurate determination of the boric acid, 

 which was made by the method proposed by Professor F. A. 

 Gooch.f The material for analysis was taken from the orig- 

 inal specimens in the collection of Professor Brush, the pur- 

 est fibers being selected, which had a specific gravity of 3*123, 

 taken very carefully on a chemical balance, after boiling in 

 water to expel the air. 



The analysis by Penfield yielded 



,tio. 



l-oo 



•974 2-05 



•99 



99-98 



The air-dry powder lost 0'34 per cent by drying at 100° C. and 

 0'90 per cent at 250° C. Regarding this water as hygroscopic, 

 the ratio of Be 2 3 : RO : H 2 =1:2:1 very closely, which fully 

 substantiates the formula of Prof. Brush, H(Mn, Mg, Zn)B0 3 . 



5. Twin Crystals of Quartz with inclined Axes. 



Two twin crystals were recently purchased by Professor 

 Geo. J. Brush, in London, labeled from Madagascar. As such 

 crystals are very exceptional, we thought that a notice of them 



* This Journal, II, advi, 240. f Am. Chem. Journal, ix, p. 23. 







Eatio. 



B 2 3 



33-31 



•476 



MnO 



38-08 



•536 



ZnO 



3-24 



•040 



MgO 



1592 



•398 



H 2 



8-53 



•472 



Loss by drying at 250° C. 



•90 





