Dana and Wells — New mineral, Beryllonite. 31 



mained in the BeO of III. which was carefully determined by 

 the molybdic method and a correction made for it. The pu- 

 rity of the weighed BeO was shown by dissolving that obtained 

 from II in HC1, evaporating off the excess of acid, dissolving 

 the residue in the least possible amount of pure NaOH solu- 

 tion and precipitating the BeO by diluting largely and boiling ; 

 the BeO obtained in this way amounted to 19*81 per cent, an 

 amount practically identical with the original weight. 



For the determination of ]STa 2 in Y and YI the mineral 

 was dissolved in HC1, P 2 6 and BeO were separated by the 

 usual methods and the metal was weighed as chloride ; the 

 results are probably about 0*7 per cent too low on account of 

 the difficulty of washing some of the precipitates. 



Relations to other species. — As has been shown above, the 

 general formula of beryllonite is analogous to that of triphylite 

 and lithiophilite, viz : 



Beryllonite. Triphylite-Lithiophilite. 



NaBeP0 4 Li(Fe,Mn)P0 4 . 



There does not appear, however, to be as close a relation be- 

 tween the forms as might be expected, although our knowledge 

 of triphylite* in this respect is scanty. The two minerals are 

 alike in having two pinacoidal cleavages, but the third pris- 

 matic cleavage of triphylite has an angle of about 47°. The 

 vertical axes, however, are nearly equal. The axial ratios are 

 _ i 



Triphylite & : b : c=0"4348 : 1 : 0-5266 001 * Oil = 27° 46' 



_ I 

 Beryllonite.. . a : b : c=0"5724 : 1 : 0-5490 001 a 011 = 28° 46' 



The optical relationsf are different except as regards the 

 size of the axial angle, for which we have 2H ar = 74° 45' 

 triphylite and 72° 35' beryllonite. 



A closer relation seems to exist to the only other phosphate 

 in which beryllium is known to exist, that is herderite. This 

 has the composition (CaF)BeP0 4 in which the univalent group 

 CaF (partly replaced by CaOH) corresponds to the sodium of 

 the beryllonite. In form the two minerals are apparently 

 related. 



Thus, we have 



Herderite. Beryllonite. 



110 a 110=63° 39' 110 ~ll0=59° 34' 



001 a 011=22° 57' 001 a 023 = 20° 61" 



001 a 031=51° 43' 001 a 021=47° 41' 



001 a 331 = 67° 27' 001 ^ 221 = 65° 39' 



001 a 362 = 58° 30' 001 „ 121 = 55° 33' 



* Of. Tschermak, Ber. Ak. Wien, zlvii, 282, 1863, and J. D. Dana, this Journal, 

 II, xi, 100, 1851. 



f Cf. Brush and Dana, this Journal, xvi, 118, 1878. 



