!>2S 



Larsen and Glenn — Minerals of the 



Table II. Analysis and molecular ratios of sine-copper melanterite from 

 the dump of the Good Hope Mine, Vulcan, near Gunnison, 

 Colo., by M. L. Glenn. 



CuO 12.37 1561 



ZnO 12.89 1581-1 X -98 



FeO 2.14 . 30J 



S0 3 28.78 360 1X1.02 



HoO 42.61 2365 7 X .96 



Insol 1.11 



99.90 



The Chalcanthite Group. 



Zinc-copper melanterite loses water rapidly in dry air 

 and alters to a fine, homogeneous aggregate of a mineral 

 that has optical properties very near those of chalcan- 

 thite, and it must be the zinc-copper equivalent of chalcan- 

 thite. A small amount of the fine powder left from the 

 analysis of the zinc-copper melanterite and kept in a room 

 two months during the winter was completely altered. 

 The sample contained 35.0 per cent H 2 while the com- 

 pound with 5H 2 should theoretically contain 36.1 per 

 cent H 2 0. The resulting product is a pale blue, finely 

 crystalline aggregate which is apparently homogeneous 

 and which has the optical properties given in column 1 of 

 Table III. In column 2 the properties of chalcanthite are 

 given for comparison; in column 3 the properties of an 

 iron-copper chalcanthite derived from the dehydration of 

 artificial pisanite ; in column 4 the properties of the sider- 

 otil derived from the dehydration of melanterite ; in col- 

 umn 5 those of artificial cobalt chalcanthite ; and in column 

 6 those of artificial manganese chalcanthite. 



Table III. Optical properties of members of the clialcanthite group. 



Zine-copper 

 chalcanthite 



Chalcanthite 



Iron-copper 

 chalcanthite* 



Siderotic 



Cobalt Manganese 



chalcanthite 8 chalcanthite 3 



Color 



pale blue 



Berlin blue 



pale green 



white 



rose pink 



pale pink 



Opt. character 



— 



— 



— 



— 



— 



_ 



2V 



mod. 



56° 



mod. 



rather large 



med. 



med. large 



Dispersion 





slight 



p > v slight 



p > v weak 



not stg. 





a 



1-513 



1-516 



1-517 



1 -526 



1-530 



1-495 



fi 



1-533 



1-539 



1-536 



1-536 



1-548 



1-508 



7 



1-540 



1-546 



1-543 



1-542 



1-550 



1-514 



7-a 



•027 



•030 



•026 



•016 



•020 



019 



a Unpublished manuscript by E. S. Larsen. 



