NATURAL SCIENCES OF PHILADELPHIA. 299 



NOTES ON FELDSPARS AND SOME OTHER MINERALS OF 

 PHILADELPHIA AND VICINITY. 



BY THEODGEE D. RAND. 



Orfhoclase, from the ravine three-quarters of a mile west of 

 Media, the locality mentioned in Dana's Mineralogy as Mineral 

 Hill. Color pale-greenish, two cleavages highly perfect, giving a 

 prism four inches, by one and a half, by one and a half, 90°. Four 

 other specimens from the same locality, one quite green, the others 

 grayish and greenish, all with two perfect cleavages, 90°. 



Oligoclase, from same locality, and intermixed with the former 

 and with quartz, but showing opalescence, and sometimes chato- 

 yant reflections, and, rarely, both on the same surface, the brachy- 

 diagonal cleavage oo P oc. These cleavages were by no means so 

 perfect as in the former, and but few specimens woiild admit of 

 accurate measurements. The basal plane generally showed dis- 

 tinct but very fine strise. The measurements are given below. 



OHgoclase, from two miles west of Media, and southwest of the 

 Black Horse Hotel. This is the whitish, translucent moonstone, 

 occurring in A^ery brilliant specimens. In this, as in the former, 

 the cleavage surface parallel to oo P oo is frequently irregular and 

 sometimes curved. There was also observed, in both this and the 

 former, a third cleavage, still more imperfect. The measurements 

 (with the common goniometer) were as follows : — 



Oligoclase, 12 3 



^^ -D^ ( 93.50 93 



OP on CO Poo I ggjO g^ gg _ 



„-D „, , ( (If 00 P' 114.40) 



OP on 3d cleavage j ^ 65.20 ... 07 67 



^. oT , ( (If odP' 120.24) 119 120 ... 



coPccon3dcleav.|^ 59.56 ... 63 ... 



1, 2, 3, and 4 are from the ravine near Media; 5, G, 7, and 8 from 

 near the Black Horse Hotel. 



It seems probable that this third cleavage, which has not, I be- 

 lieve, been noticed before, is parallel to the plane co P' (I' of 

 Dana), similar to that of orthoclase and albite. 



Sunstone, from a ravine immediately north of that first de- 

 scribed, 90°. Near this the Delawarite is found. My specimens 

 18t2.] 



