478 



SMITHSOXIAX MISCELLANEOUS COLLECTIONS 



VOL. 52- 



bination of this form and the cube a (lOO), which gives rise to 

 overlapping strips or laminse parallel to (lOo) and bounded by (210), 

 each lower strip being usually a bit broader than the one above. 

 The ordinary arrangement across the laminations is: A smooth sur- 

 face parallel to the cube face, i to 2 mm. in width ; a series of steps 

 down across alternations of cube and pyritohedron for about i mm. ; 



Fig. 81. — Pyrite cube with crystallized gold and galena. Natural size. 



a flat-bottom valley i to 2 mm. wide; a course of steps up for i mm. 

 to a second plane surface, and so on. Frequently a narrow strip 

 extends only partly across the cube face when, cut off by two octahe- 

 dral planes, it ends in a dull point, and the strip beneath continues 

 until it perhaps is terminated by similar bounding planes. Scharff^ 



' Scharff, F. Ueber die Bau-weise der Wiirfel-formigen Krystalle. Neues 

 Jahr. f. Min., etc., 1S60, pp. 385-425. See especially p. 412 and Figs. 41, 43, 47, 

 Plate VI. 



