PROCEEDI^^GS OF THE NATIONAL MUSEUM. 



VOL. 63. 



Three crystals were measured in detail, and upon these 39 forms 

 were found, 7 of which are new for the species. These 3 crystals 

 are represented as nearly as practicable in their actual development 

 in the Figures 1 to 3. The terminal faces of crystal 1 are highly 

 lustrous, but all of the larger- faces are marked by discontinuous 

 grooves parallel to the plane m (ITO) in the drawing. On crystal 2, 

 the p3^ramidal faces are all horizontally striated by reentrant angles, 

 while the dome (021) has two sets of striations parallel to (110) and 

 (TlO) meeting down the center of the face. All of the faces in the 

 prismatic zone are deeply striated. These striae do not, however, 

 produce any rounding of the angles, but they consist of minute and 

 very sharp reentrant angles. Thus, a single sharp and brilliant 

 signal may result from simultaneous reflection from half a hundred 

 narrow lines in exactly parallel position. In this respect the draw- 

 ings are greatly generalized, only the major repetitions and reentrant 

 angles being shown. 



In the following table are given the averages of the angles measured 

 on the three crystals: 



Forms and angles on stephanite. 



