A. J. Moses — Crystallization of Molybdenite. 359 



Art. XXXII. — The Crystallization of Molybdenite; by 



A. J. Moses. 



The only satisfactory measurements of molybdenite crystals 

 which have been made are those of Brown* upon material 

 from Frankford, Pa. The earlier measurements of Homes 

 were discredited by Kenngott's later examination and those of 

 Knop were evidently made upon bent crystals. 



The difficulties in the way of measurement are the striations 

 upon the pyramidal faces which produce multiple and blurred 

 images of the collimator signal and the frequent bending of the 

 crystals as shown by grooves and ridgesf upon the cleavage 

 surface which frequently form three systems, each perpendicu- 

 lar to an edge of the hexagonal surface. In some cases these 

 grooves are at many angles without any apparent law. 



In a careful examination of a number of molybdenite crystals 

 I have obtained some results which are worthy of record. In 

 some cases, as in the Warren, N. H. crystals, the interpretation 

 of the results may not be the correct one. 



1. Molybdenite from Enterprise, near Kingston, Ontario. 



In a quantity of material obtained from Mr. C. W. Dickson 

 there was one doubly terminated crystal (fig. 1), about 8 mm 

 . across by 2 mm thick, the pyramidal faces of which were bright, 

 a little curved and almost free from striations, and the terminal 

 plane, which did not appear to be a cleavage, was bright and 

 showed few grooves. 



The crystal was attached to a gangue of pyroxene, phlogopite 

 and pyrrhotite but projected so that it was possible to measure 

 the angles between the basal plane and two of the pyramidal 

 faces. 



The faces did not yield single images and two separate 

 adjustments were made for each angle with different combina- 

 tions of lenses. The results, each in itself an average of four 

 or more measurings, were : 



First angle. Second angle. 



41°21|' 41° 28' 



41 53 41 02 



Average of all, 41° 26'. 



This corresponds to a pyramid (2025) the angle for which cal- 

 culated to Brown's unit would be 41° 23'. 



*Proc. Acad. Nat. Sci. Phila., 1896, p. 210. 



f Brogger showed (Zeitschr. f . Kryst. x, 507, 1885) that such markings 

 could be produced by pressure, and Miigge attributed them (N. J. f. Min. 

 1898 i, 109) to translation along the plane 0001 perpendicular to the markings. 



