370 



HAROLD L. ALLING 



Sjogren^ and Strandmark^ studied celsian, the latter proving 



that celsian and orthoclase form an isomorphous solid solution series 



called hyalophane. 



TABLE VI 



Cassinite, Blue Hill, Delaware County, Pennsylvania 



* Approximate, spectroscopic determination. 



Analyses i and 2: Penfield and Sperry, Amer. Jour. Sci. (3), XXXVI (1888), 324. 

 See Da.na., System of Mineralogy, p. sT-g- 



Analyses j and 4: Made for the writer by H. B. Croasdale of the Fraser Labora- 

 tories, New York City. 



Penfield and Sperry^ have described a barium-bearing perthitic 

 feldspar from Blue Hill, Delaware County, Pennsylvania.'* Their 



' Hj. Sjogren, Geol. Foren. Fork, XVII (1895), 578. 



^]. F. Strandmark, Geol. Foren. Fork., XXV (1903), 289; XXVI (1903), 97; 

 Zeitschr.f. Kryst. Min., XLIII (1907), 89. 



3 S. L. Penfield and Sperry, Amer. Jour. Sci. (3), XXXVI (1888), 324. 



iDana, A System of Mineralogy, p. 319: "A duU bluish-green sub transparent 

 kind, of an aventurine character, from Blue Hill, 2 mUes north of Media, Pa., cassinite." 

 P. 322: "Cassinite of Lea from Blue Hill, Delaware Co., Perm.; shown by Penfield 

 to be a monoclinic feldspar (extinction on b=^ 6°) with albite running through it in 

 thin tapering plates parallel to the orthopinacoid. The analysis corresponds to 35 p. c« 

 albite, 51 p. c. orthoclase, and 13 p. c. of BaAl2Si40i2." This formula is incorrect. It 

 should be BaAlaSiaOg. 



