356 O. C. Farrington — Studies of Brazilian Favas. 



Avater present is small but is characteristic and easily detected. 

 This constituent thus makes a distinguishing- character between 

 these favas and rutile or any other of the titanium oxides. 

 The writer therefore proposes the term jparedrite from the 

 Greek 7rdpe8po<;, an associate, for these favas. The term refers 

 to the fact that they are companions of the diamond. 



The favas of brighter luster and lower specific gravity in 

 the so-called " goyazite " were found to be for the most part 

 easily fusible B. B. Generally also they gave a green flame, 

 indicating the presence of barium or phosphoric acid or both. 

 They also generally gave off acid water in the closed tube. 

 These properties indicated that the pebbles belonged to the 

 group of phosphate favas described by Hussak ;* although 

 Hussak unfortunately gave no blowpipe characters. They 

 were only slightly decomposed by HC1, but after fusion with 

 JSTa 2 C0 3 were readily and completely dissolved to a golden 

 yellow solution. In order to still further determine the char- 

 acters of these pebbles, quantitative analyses were made of 

 three of them by Mr. H. W. Nichols with results as follows : 



1 2 3 



P 2 5 18-33 



Al 9 O s ._ 40-56 



Fe 2 3 2-30 



BaO 13-84 



CaO 1-S1 



MgO 



MnO 



Na 2 0.. 3-75 



Si0 2 3-54 



so 3 



H 2 14-89 



F 0-40 



Moisture 0-65 



100-07 

 O = F 2 0-17 



99-90 

 G = .- 2-99 



The analyses show that these favas are related in composi- 

 tion to the mineral gorceixite described by Hussak. f He 

 deduced the formula BaO(Ca,Ce).2Al 2 3 .P 2 Q 5 .5H 2 for this 

 mineral from the following analysis, the analysis having been 

 calculated to 100 after deduction of SiO„, Fe 2 3 and Ti0 2 : 



*Tsch. Min. u. Petr. Mitth., xxv, 334-335, 1906. 

 f Loc. cit. 



22-56 



31-62 



29-98 



29-87 



2-23 



2-00 



21-48 



20-61 



1-95 



0-13 



1-58 





tr. 





4-23 



0-74 



2-22 





1-31 





12-31 



13-67 





1-77 





0-26 



99-85 



100-67 





0-74 





99-93 



3-10 



3-17 



