Silver and on the CrystallizaUon of Polyhasite. 21 



from it on to similar adjacent forms. The prism I, 310 is 

 often developed about equal in size to 5, and with the latter 

 would correspond in rhombohedral symmetry to a hexagonal 

 prism of the second order. The prism A, 130 and the hori- 

 zontal prism ^, 021 were found together on onlj one crystal as 

 small faces symmetrically located with reference to the pina- 

 coid h. 



rig. 1 shows the prevailing type of crystal, with hexagonal 

 aspect, the characteristic triangular markings on the basal 

 plane, but with only the most prominent of the bevelling faces 

 present. Two fragments were found which in habit were 

 essentially like fig. 2. These had a decidedly monoclinic habit 

 and were the most free from striations, vicinal faces and indi- 

 cations of a possible twinning of any crystals that were 

 observed, and from them the fundamental measurements pre- 

 viously given were obtained. 



A few crystals were quite remarkable for their size, the hex- 

 agonal plates being 3^°" in diameter and V"^ thick, but they 

 were coated with druzy quartz and could not be used for crys- 

 tallographic measurement. The specimen showing the largest 

 <;rystals was presented by Mr. Bayliss to the author for the 

 Brush collection at JN"ew Haven. The crystals from which the 

 measurements were obtained averaged less than 4™°^ in diam- 

 eter. 



The following list includes the forms which have been 

 observed, but, as already stated, twinning may account for a 

 similar form being found modifying both the acute and obtuse 

 angles of the crystals and being repeated in the zones between 

 c and a and c and m. 



a, 100 



d, 102 



f, 201 



s, 221 



5°, 221 



h, 010 



n, 101 



e\ 401 



11, 331 



If °, 331 



c, 001 



t, 201 



/°,601 



o°,n4 



X, 311 



I, 310 



e, 401 



0, 114 



^°,113 



y, 313 



m, 110 



/, 601 



r, 112 



'r°, 112 



z, 31-12 



A, 130 



Z/, 203 



p, 111 



p%lll 





k, 021 



n°,I01 



V, 332 



v°, 332 





The forms 



correspond: 



ing to these found by Mier 



s^ on poly- 



basite are <?, m, 7^, ^, ^, 5, 



r and lo, 109. 











*Loc. cit. 



* 





