Jan. 19, 1877.] 



509 



[KOnig. 



Contributions from the Laboratory op the University of 



Pennsylvania. 



No. VII. 



On astrojJhylUte, arfvedsonite and zircon, from El Paso Go. Colorado, and 

 a colorimetric estimation of titanium before the blow-])ipe. 



By George Augustus Konig, Ph. D. 



{Bead before the American Philosophical Society January 19th, 1877.) 



General occuri'ence. The three minerals are imbedded in quartz. On the 

 specimens which I examined no orthoclase, nor any other species could be 

 found ; yet the mother rock may be presumed to be a very coarse grained 

 granite or syenite. Until satisfactory information is received on this point, 

 it must, of course, remain doubtful. In stating that the three minerals occur 

 together, it is but right to say, that I make a hearsay statement. 



For, the specimens of quartz in which astrophyllite and zircon abound, 

 are destitute of arfvedsonite, and the specimen on which the latter is abun- 

 dant, does not show either of the two other species. But the character of 

 the quartz, as the common matrix, is strictly identical throughout, of 

 grayish color, locally stained with iron ochre, and massive in structure. The 

 co-occurrence of these three species, at once calls up the close similarity 

 with that of Brevig in Norway, the only locality at which astrophyllite 

 was known to exist. The only difference being that orthoclase forms the 

 matrix at Brevig, and quartz in Colorado. 



To Dr. Foote, of this city, I am indebted for the material of this investi- 

 gation. 



I. Astrophyllite. 



Qeometrical properties. The crystals exhibit elongated prismatic forms, 

 the cross section being nearly a rectangle on the majority of the individuals. 

 I succeeded in finding some crystals, however, whose section is more com- 

 plicated and with which I endeavored to establish the angular relations be- 

 tween the several faces. No terminal development of any kind could be ob- 

 served ; the crystals appear all broken across the direction of main extension. 



The measured edges are, therefore, all in one zone. The figure repre- 

 sents a cross section of the best developed crystal, and the faces are desig- 

 nated a, b, c, etc., solely in reference to their sequence. 



a A c = 180O 15' 

 aAe=: 93° 

 A e = 870 

 d A e = 1190 

 b A c = 1490 30' 

 c A <i = 1480 



proc. amer. philos. soc. XVI. 99. 3l 



