274 



University 



of California . 



[Vol. 3. 



ine-purple, b = pale pink or amethyst, C = colorless. The C 

 ray is absolutely colorless no matter how thick the crystal is. 



The average of a number of determinations of the inclination 

 of the acute bisectrix to the vertical axis, gave, for sodium light, 

 jB* a Ac= +25° 24' That is, the acute bisectrix lies in the 

 obtuse angle /? and is nearly normal to the basal pinacoid 

 (Dana's orientation) . 



The indices of refraction, a and y were determined by the 

 method of Due de Chaulnes on a crystal about a centimeter in 

 thickness. The values obtained, the average of a number of 

 readings, are only approximate, though they agree remarkably 

 well with the determinations of Des Cloizeaux. The results 

 obtained by the writer for sodium light, are: 



This gives, as the strength of the double refraction, 

 y — a = .027. The results of Des Cloizeaux are: 



Many attempts were made to prepare a section of the mineral . 

 normal to the acute bisectrix but it invariably went to pieces, 

 owing to the highly perfect prismatic cleavage. 



The average of several analysis of the mineral afforded the 

 writer the results shown in column I. In the second column is 

 given an analysis of the pink spodumene from Branchville, 

 Conn., analyzed by Professor S. L. Penfield.* Unfortunately 



a = 1.652 

 7 — 1.079 



Na 



a = 1.651 

 y — 1.677 



CHEMICAL COMPOSITION. 



I. 



SiO,. 



A1 2 3 



Mn 2 On 



Li 2 



Na.0 



K 2 



Fe a 3 



CaO 



MgO 



Ign. 



no loss 



04.42 

 27.32 

 0.15 

 7.20 

 0.39 

 0.03 



none 



none 



none 



7.C2 

 0.39 

 trace 

 0.20 



0.24 



99.51 



99.90 



*Loc. cit. 



