244 Penfield and Ford — Calaverite. 



Considerable time has been devoted to the study of the zonal 

 relations of calaverite, with the results shown in the stereo- 

 graphic projection, figure 30, whicli may be summarized as 

 follows : 



1. D (304), *(10-M1), p (111), n (11-14-10), o (13-22-10), 

 # (11-29-5) and $(11-62-6). Symbol of the zone (4 1 3). This is 

 the principal zone, and almost the only one which is apparent on 

 simple inspection of the crystals. A possible simpler symbol for 

 s is (2-11-1), also in this zone, but most of the measurements indi- 

 cate the more complex symbol. 



2. D (304), /(112), £(4-M0), v (2-11-10) and t (13-20-4). 

 Symbol of the zone (4 2 3). 



3. c(001),/(112), p (111), m(110) and 10 (111). Symbol of 

 the zone (1 1 0). 



■4. m (110), &(l0-32-21), w (Til), i (756), and N (201). Sym- 

 bol of the zone (112). 



5. M (101), g(-i'1']0) i p (111) andp (44-21-2). Symbol of the 

 zone (121). 



6. m (110), n (11-14-10) and g (4-7-10). Symbol of the zone 

 (10-10-3). 



7. m (110), o (13-22-10), v (2-11-10) and M x (9-0-10). Symbol 

 of the' zone (10*10-9). 



8. .#(801), q (11-29-5), a (2-10-1) ? and m(I10). Symbol of 

 the zone (118). 



9. _^ (17-0-2), s (11-62-6) and m (110). Symbol of the zone 

 (2-2-17). 



10. B a (901), ^(111) and v (2-11-10). Symbol of the zone 

 (189). 



11. b (010), s (11-62-6), x (11-20-6) and N x (H'0'6). This is 

 the only case where two pyramidal forms have been observed in 

 a zone between b and a form in the striated zone. Furthermore 

 it is exceptional to find forms in the striated zone having the 

 same vertical circle angles as the pyramids. 



In addition to the foregoing there are a number of very 

 close approximations to zones, some of whicli are indicated by 

 dashed great circles in figure 30. These are drawn from (901) 

 and (1*0-4), and although probable zonal relations seem to be 

 indicated by the projection, the symbols assigned to the forms 

 do not quite satisfy the zonal equations,, and possible changes, 

 indicating greater simplicity of the symbols, do not suggest 

 themselves. 



Chemical relations of Sylvanite and Calaverite. — Both 

 minerals conform to the general formula [Au,Ag]Te 2 , silver 

 being regarded as isomorphons with gold. In sylvanite the 

 proportion of gold to silver is near 1:1, so that the formula 

 may be written AuAgTe 4 . The percentage of silver 



