420 Palache — Notes on Tellurides from Colorado. 



A skeletal development, well known on sylvanite from 

 other localities, is common on these crystals ; but it did not 

 affect the character of the crystal planes which were in general 

 brilliant, giving good reflections. 



Measurements were made on the two-circle goniometer and 

 the adjustment of the crystals was rendered very accurate by 

 the use of the three pinacoids, nearly always all present. 



The following twenty-nine forms were observed on the five 

 crystals measured : 



c, 



001 



m, 



101 



r, 111 



u* 



723 



a, 



100 



n, 



201 



w* 343 



n, 



341 



b, 



010 



N, 



201 



s, 121 



y, 



123 



R, 



120 



d, 



011 



o, 131 



p> 



111 



e, 



110 



V* 



525 



q, 141 



0", 



121 



A 



210 



y, 



212 



i, 321 



J\ 



321 



9, 



310 



t, 



323 



j* 521 





521 



123 



In the following table are given the computed and measured 

 angles for the four new forms. The forms o, 131, q, 141 and 

 II, 341 while not new, have not been observed since Miller's 

 studies, and are here added, with their computed angles, in 

 order to complete the tables of Goldschmidt by whom they 

 were omitted as uncertain. The new form u, 723, is the most 

 interesting, occurring in nearly all the measured crystals with 

 good development and being apparently characteristic for this 

 localit}\ 





Miller 

 symbol. 



Computed 

 angle. 



Average 



measured 



angle. 



Yariations. 



Number 



of 

 observa- 

 tions. 



Quality 





<P 



P 



<P 



P 



* 



P 



of 



Letter. 



+ 



— 



+ 



T' 



3' 



faces. 



V 



525 



57°'06' 



39°-4l' 



57°-03 7 



39°-36' 



12' 



13' 



5 



fair 



to 



343 



24-53 



58-52 



24-49 



58-57 



9 



8 



7' 



6 



2 



poor 



u 



723 



65*04 



60-42 



65-01 



60-36 



14 



5 



12 



15 



6 



good 



3 



521 



56-53 



76-22 



56-50 



76-25 











1 



excel- 



n 



341 



24-44 78-36 

















lent. 







131 



11-39 73-50 



















9. 



141 



8-47 177-38 



















The figures illustrate the typical prismatic habit, as shown in 

 various combinations of planes. In fig. 1 the pyramids are 

 developed at the expense of orthodome and clinopinacoid ; in 

 fig. 2 the latter forms predominate, giving a tabular-prismatic 

 character to the crystal. This zone of pyramids is generally 



* Forms marked thus are new. 



