из 



In thin laminae the mineral is colourless. Thicker plates 

 are of yellowish colour faintly inclining to green. The faces 

 of the third pinacoid display a fine pearly lustre. In parallel 

 polarized light cleavage plates show total extinction parallel and 

 perpendicular to the second pinacoid. In the conoscope the 

 same plates show a biaxial interference figure. The plane of 

 the axes is parallel to the second pinacoid. The acute bisectrix 

 makes in front of the c-axis an angle of about 7° with this 

 axis. The apparent axial angle, 2E, as determined by the 

 micrometer ocular and Schwartzmann's scale, is about 60°. 

 The double refraction is negative as in all other micas. 



The specific gravity of the mineral was found, by .weighing 

 in benzole, to be 2,701. Hardness = 2,5. The mineral is 

 tough, but not very elastic. Its cleavage is not quite so per- 

 fect as with most other micas. Only with difficulty can the 

 mineral be pulverized. 



Before the blowpipe it fuses easily to a colourless, 

 blebby glass, imparting an intense red colour to the flame. 

 It is not perfectly decomposed by any acid other than hydro- 

 fluoric acid. 



The analysis was made by myself on three different por- 

 tions of the material. In the first, which was subjected to an 

 alkaline carbonate fusion, SiOo, Al„0.^, Fe^O.^^ and MnO 

 were determined. In the second, which was brought into solu- 

 tion by a mixture of hydrofluoric and sulphuric acids, the alkalies 

 Avere determined, the lithium being separated by amylic alcohol 

 according to the method of Gooch^. The fluorine was deter- 

 mined in a third portion, which was fused with soda according 

 to the method of Berzelius. The analysis yielded the fol- 

 lowing result. 



Bull, of the U. S. Geol. Survey. No. 42, 1888, p. 73, 

 .XIV. S 



