G. Palache — Mineralogical Notes. ' 257 



The somewhat complex symbols of the pyramids are sup- 

 ported by concordant measurements and by the simple and 

 normal zonal relations existing between them. The choice of 

 the pyramid r as unit would simplify the pyramid symbols 

 slightly, but there would then be no unit prism and the relation 

 in form to chalcocite would be obscured. 



The table which follows presents the calculated and measured 

 angles with the range of variation (in minutes) of each form. 

 The measurements were made on the two-circle goniometer. 



Sym- 

 bol 



Calculated 



Measured 



Limits (in 



minutes) 



No. of 





<P 



P 



t 



-> 

 P 



4> 



P 



vations 



> Quality 



c 001 







00°00' 



_ _ 



00°00' 













5 



good 



b 010 



00°00' 



90 00 



00°00' 



90 00 



0'to + 7' 



— 





•8 



Fail- 



a 100 



90 00 



90 00 



89 57 



90 00 



-27 to + 7 



— 





8 



fair 



m 110 



60 12 



90 00 



60 12- 



90 00 



-5 to + 5 



— 





10 



good 



I 130 



30 12 



90 00 



30 11- 



90 00 



-9 to + 9 



— 





6 



poor 



f 012 



00 00 



25 43- 



00 03 



25 36 



to +12 



-23'to +14' 



3 



faii- 



g on 



00 00 



43 56- 



00 00 



43 55- 



to + 7 



-2 to + 



3 



7 



good 



d 021 



00 00 



62 34- 



00 11 



62 40 



— 



— 





1 



faii- 



y 103 



90 00 



29 17 



90 00 



29 17 



to +12 



-5 to + 



5 



6 



good 



p 111 



60 12 



62 43 



60 10- 



62 43 



-5 to + 6 



-3 to + 



o 



12 



very good 



o 236 



49 20 



36 29 



49 19 



36 33- 



-11 to +12 



-4 to + 



7 



7 



fail- 



r 233 



49 20 



55 56 



49 24 



55 57 



-7 to + 7 



-6 to + 



8 



6 



fair 



s 263 



30 12 



65 51 



30 11- 



65 51* 



-8 to + 9 



-9 to + 



7 



9 



good 



t 136 



30 12 



29 08 



29 20 



29 12 



— 



— 





1 



fair 



u 1-9-12 



10 59 



36 22 



11 12 



36 30 



— 



— 





1 



srood 



The axial ratio was calculated from the measurements of 50 

 best faces of 12 forms on 5 crystals. The average values of 

 the closely accordant results differ but slightly from the ratio 

 determined by Hussak. 



a :~b : c = 0-5725 : 1 : 0-9637 (Palache). 

 = 0-5734 : 1 : 0-9649 (Hussak). 



The angles calculated from this ratio in the form of the 

 Winkeltabellen of Goldschmidt are given in the table of 

 measurements above. 



As pointed out by Hussak, chalmersite stands in close 

 relationship to the chalcocite group of minerals both in compo- 

 sition and form. If we also include in this group the mineral 

 pyrrhotite, recently shown by the magnetic studies of Kaiser* 

 to be orthorhombic and pseudohexagonal through twinning, and 

 if we calculate its ratio from the angle for the pyramid 2021, 

 using Seligman's value as the most reliable observation yet 



* Kaiser, E., Die Krystallform des Magnetkies, Centralb. fur Mineral, 

 1906, 261. 



