220 sS. L. Penfield and G. S. Jamieson — Tychite. 



An analysis of the purest material, separated by means of 

 the heavy solution, gives the formula 2MgC0 3 . 2Na 2 C0 3 . 

 ]N T a 2 S0 4 , the results being as follows : 



I. II. Theory. 



S0 3 . . .' 15-08 15-06 15-33 



C0 2 ..33-55 33-45 33*72 



MgO 15-83 15-77 15-33 



NaO 35-49 35'65 35*62 



99-95 99-93 lOO'OO 



The slight discrepancies between the results of the analyses 

 and the theory are probably to be accounted for by the pres- 

 ence in all of the crystals of the minute inclusions mentioned 

 on the previous page. 



The finely powdered salt does not dissolve to any extent in 

 hot water, nor does it suffer decomposition. Some powder, 

 boiled with water for a considerable time, then filtered and 

 dried, gave the following results : — S0 3 , found 15*21 per cent, 

 theory 15*33 per cent. The filtrate gave only a slight reaction 

 of a sulphate when tested with barium chloride. 



Name. — "We have named the new and rare sulphate tychite, 

 from rvxVi meaning luck or chance, a name which it well 

 deserves, when it is considered that out of fully five thousand 

 specimens examined, the very first crystal and one of the ten 

 last crystals tested proved to be the sulphate, and only two 

 other specimens were found, the ones lost in an unsuccessful 

 attempt to make an analysis. 



Comparison of the artificial salt with the natural mineral. — 

 Without question, the artificial salt is identical with the mineral 

 found at Borax Lake: they both contain the same constitu- 

 ents. They crystallize not only in the same system, but also in 

 octahedrons. They are isotropic, although the last crystal of 

 tychite found showed some slight action on polarized light, 

 which seemed to be confined only to the exterior portions of 

 the crystal, for fragments from the interior were wholly iso- 

 tropic. The specific gravity of the artificial salt is 2*588, of 

 the crystal examined by Pratt (the analysis of which was lost) 

 2*456, and of the last crystal found by us 2*30. The last crys- 

 tal, however, contains numerous inclusions, which undoubtedly 

 account for its low specific gravity. As far as can be recol- 

 lected, the crystal examined by Pratt was very white and pure, 

 but not equal in transparency to the artificial crystals. Both 

 Pratt's determination, 2*456, and ours of the artificial salt, 

 2'588, are somewhat higher than the specific gravity of 

 northupite, as might be expected from differences in composi- 

 tion : Pratt found the specific gravity of northupite to be 



