476 



PALACHE AND SCHALLER: HODGKINSONITE 



The forms observed are c(OOl), m(llO), s(Oll), r(221), i(401), 

 x(305), g(552), it(322). The last four of these forms were found 

 only on the etched crystals, which had been measured with con- 

 siderable care before the better crystals were found. These four 

 high-index forms are no doubt vicinal and due to etching of the 

 crystals; they are nevertheless retained in the table of measure- 

 ments and a figure showing them is given since they are charac- 

 teristic of most of the specimens. 



In the following table may be found all the observations made 

 on these crystals, together with the calculated angles for the 

 various forms. 



TABLE 1 



Angle Table for Hodgkinsonite 



The crystals are acute pyramidal in habit as shown in figure 

 1, and are dominated by the equal development of unit prism 

 m and pyramid r. On the etched crystals this pyramid is re- 

 placed by a group of facets whose average position corresponds 

 to the symbol (552). The clinodome and prism faces are always 

 smooth but often dull and poorly reflecting. The faces of other 

 forms are minute and of the poorest quality. Figure 2 shows 

 one of the etched crystals, doubly terminated and with the small 

 faces of uncertain forms characteristic only of specimens of this 

 type. 



The perfect cleavage of hodgkinsonite is parallel to the basal 

 pinacoid. The density is 3.91, determined by a pycnometer on 



