Knopf and Sch alter — Two New Boron Minerals. 331 



Eatios 



FeO -618) .__ 



MgO ... -036 f bU ° 



Fe,O a -105 -97 



H.,0.. -113 1-04 



B 2 "0 3 "298 2-74 



These ratios lead to the formula 6(Fe,Mg)O.Fe 2 3 .H 2 0.3B 2 3 . 



The methods of procedure were similar to those described 

 for hulsite. The reason for the single high value for ferrous 

 iron (45 - 82 per cent) is not known, but as the other three 

 values agree well, the average of all four is taken rather than 

 to give preference to the single higher value, which may be 

 due to error in the manipulation. ( See footnote on page 328 

 for reference to the ferrous iron and water determinations. ) 

 The value here given for FeO includes that of the vesuvianite 

 present, but it is probably so small that it may be neglected. 

 While this mineral has not yet been analyzed, the ferrous iron 

 in the 14 per cent vesuvianite present is doubtless less than .3 

 per cent. The effect of the arsenopyrite was probably nil, as 

 the mineral particles were so large that the arsenopyrite 

 remained undissolved in the hydrofluoric acid solution. Of 

 the insoluble material about 1*20 per cent was arsenopyrite, 

 the remainder being vesuvianite. The boric acid determina- 

 tion is probably too low. 



The density of the sample analyzed was determined as 4*544. 

 By calculation the density of pure paigeite is found to be 4'7l, 

 the sample analyzed consisting of the minerals in the pro- 

 portion shown below : 



Vesuvianite, density 3*40 = 13-75 

 Arsenopyrite " 6-0 = T20 



Paigeite " 4-71 = 85-05 



100-00 



While these two minerals are very similar in composition, 

 there is sufficient difference between them to preclude their 

 being referred to the same species. The mode of occurrence, 

 the hulsite in stout crystals, the paigeite in long hair-like 

 needles, and the general appearance of these two minerals 

 render it very easy to distinguish them on sight. The only 

 borates known of analogous composition to these new minerals 

 are ludwigite, pinakiolite and warwickite, of which only the first 

 is similar in composition, this being 4(Fe,Mg)O.Fe 2 3 .B 2 3 . 



