382 Prof. B. Silliman, Jr.> on some American Minerals. 



not so easily separable as in mica. Hardness 3. G. 2*963. Lus- 

 tre of sides faint pearly, of basal plane very brilliant pearly, re- 

 sembling Heulandite, but perhaps more brilliant even than in 

 that species. Color of cleavage face pure white, of sides grayish, 

 sea green or whitish. Laminae rather brittle, inelastic, and quite 

 transparent. 



B. B. Exfoliates, fuses on edges of thin laminse and emits a 

 stronger light than either of the corresponding species. In the mat- 

 rass, it evolves water and gives a reaction for fluorine. No re- 

 action for lithia or boracic acid was obtained, but it gives a soda 

 yellow to the flame. 



The qualitative analysis of this mineral gave silica, alumina, 



lime, magnesia, soda, water, and fluorine. 



The quantitative analysis was conducted by Mr. J. J. Crooke, 

 and gave on fusion with carbonate of baryta the following results, 

 viz., quantity taken, 1*378 gramme, found 



Oxygen. 



Si -538=perct. 39-042 = 20-28 m 15 



Al -708 " 51-378 23-99 18 



Ca -044 " 3193 r 0897 



Mg -015 " 1088 < -421 £ 154 1 



Na -012 " 0-871 I -223 



H 063 " 4-593 4-08 3 





1-380 100165 



This gives the following as the theoretical composition of the 



mineral. 



5 atoms silica = 2886-55 = per ct. 39-02 



6 " alumina = 385400 " 52-10 



1 CaMg = 31938 " 4 32 



3 « water = 337-44 " 4-56 



7397-37 10000 



The following formulas therefore express its constitution 



**» ••• * • t t 4 # III 



Si 5 Al« R+H3=R Si+2AP Si 3 +3H. 



The alumina obtained in this analysis (as well as in all the 

 others also) was very critically examined for zirconia, but without 



success. 



The black tourmaline which is associated with euphyllite has 

 left the impression of its crystals on the lateral face of the mineral 

 with such a smooth hard looking surface that it shows no trace of 

 a micaceous structure. The tourmaline has an uncommon form, 

 the faces R of the primary form being rudimentary from the ex- 

 tension of the tangential plane, truncating the summit. 





