1880.] NATURAL SCIENCES OF PHILADELPHIA. 243 



that in order to exhibit this properly, the section must be 

 exceedingly thin. He stated tliat an optical examination had proved 

 that the direction of the main lines of the markings corresponded 

 with or was at right angles to that of the crystallographic axes of 

 the Muscovite. He exhibited a plate of the mica shown distinctly 

 to be a twin by the two different groupings of Magnetite markings. 

 Examination in the polariscope confirmed this structure. Thus, 

 frequently, the crystalline structure of the mica and the direction 

 of its axes may he ascertained b}' an inspection of these markings 

 alone. It appeared, therefore, that the form and direction of the 

 markings was determined, not by independent crystallization of 

 the Magnetite forming them, but in part at least by the Muscovite 

 from which it had probably been derived. These markings are, in 

 some respects, pseudomorphs after Muscovite. He thought that 

 the statement in Dana's Mineralogy (p. 150), referring to these 

 markings, that "the brandling at angles of 60° indicates com- 

 position parallel to a dodecahedral face," was misleading, implying 

 that this form was produced by an inherent property of the Mag- 

 netite, and not, as he thought now appears, by the crystalline 

 structure of the Muscovite. 



September 24, 1817. 



A New Local if y for Asholite. — Mr. Lewis stated that he had 

 found Asbolite at Flourtown, Montgomery Co., a new locality for 

 this mineral. It is found in iron ore mines as an incrustation 

 upon Psilomelane. It is of a bluish-black color, is as soft as 

 graphite, and gives a shining streak when scratched by the nail. 

 The blowpipe indicates a considerable percentage of cobalt. 



A New Locality for Fluorite. — Mr. W. W. Jefferis stated 

 that a few days since he was shown a massive specimen of Fluor- 

 6;par of a deep purple color, which was found in the limestone 

 near the village of Howellville, in Tredyffrin Township, Chester 

 County, Pa. This is the third locality of fluor in this county. 



Epidote in Molybdenite. — Mr. Lewis mentioned that while 

 examining some Mol3'bdenite from Frankford, Phila., he had 

 found plates of a transparent hard mineral, of a light greenish- 

 yellow color, somewhat resembling Wulfenite, occurring in thin 

 laA-ers and minute scales between the folife of the Molybdenite, 

 and sometimes coating it as a thin film. It was not until after a 

 careful examination that it was proved to be Epidote in an 

 unusual form and situation. 



October 22, 1877. 



A New Locality for 3Iillerite. — Mr. Theo. D. Rand announced 

 the discovery of Millerite in Dolomite, from the Soapstone quarry 

 on the Schuylkill, in Philadelphia, near the Montgomery County 

 line. It occurred in capillary crystals in cavities of the Dolomite. 



