Pogue and Goldschmidt — Quartz from Alexander Co. 419 



Measured— Des Cloizeaux (p. 528) ; e\: e\l =-\0: -^0=24°49' 



Rath (p. 159); -R:— 8 T 3 -R=- 10: -\ 3 -0 = 25 03 -24°55 



Calculated for — 10 : — - \$-0 =24 55 



Calculated for —10: ~^0 =24 46 



Therefore — -^O appears as certain ; — - 2 T 3 -0 as questionable. 



it: = + - 1 ^-1 belongs to the following zone section: 



Letter u. It: y. 



Symbol pq = +31 + -V-1 +41 



p-3= J 1 



■y 



L — v 







Therefore + -'/-I passes well in the series. 

 For «• — — -V- 1 we have the following : 



Letter 







IV 



Symbol 



pq 



- 



- 31 





S-p 



= 









V 











in 



if 2 l) 



V-l -11 -41 

 jl ± 1 



3 2 J - 



1 



co 



1-v 



— -V 1 also passes well in the series. 



The positive and negative rhombohedrons ( + 10 and —10) 

 were determined by etching with hydrofluoric acid, and to 

 avoid injuring the specimens the following -procedure was 

 adopted. 



Crystal 1 belonged to a series of crystals of such similar 

 development that, without danger of error, one of the others 

 was employed for etching. Crystal 2 not permitting of such 

 determination by analogy, the six rhombohedron faces ±10 

 were accurately cut upon its lower, undeveloped end, by the 

 aid of a grinding goniometer.* These artificially developed 

 faces were then etched in the ordinary way, the natural faces 

 being protected by a coating obtained by dipping the upper 

 portion of the crystal in a mixture of molten sulphur and fluor- 

 spar. Such a melt was used for a similar purpose by Ph. 

 Hochschildf in a recent investigation on sphalerite. 



It finally remained to determine optically the right- and left- 

 handed character of the two crystals by observing the nature 

 of the light rotation in basal section. This was effected with- 



* The description of this apparatus has not yet been published. 

 fNeues Jahrb. f. Min., etc., Beilage-Band, vol. xxvi, pp. 209-210, 1908. 



