538 AUSTIN F. ROGERS 



chrysocolla and all other impurities. The ratios seem to show an 

 excess of both silica and water over that required for the usually 

 accepted empirical formula (H 4 CuSi0 5 ) for chrysocolla, which 

 probably indicates that cornuite is a solid solution of cupric oxid, 

 silica, and water. 



Probert 1 describes a "jelly of the most beautiful shades of 

 blue and green" with the following composition: 010 = 47.46; 

 Si0 2 =2i.2o; H 2 0=28.o5; CaO=i-39; Al 2 3 =tr., from the 

 200-foot level of Ray Central mine at Ray, Arizona. Here we 

 evidently have cornuite in process of formation. 



Chrysocolla is sometimes considered to be an amorphous mineral, 

 but while chrysocolla shows colloidal structures it is microcrystal- 

 line (metacolloid) , and recently Umpleby 2 has described crystallized 

 chrysocolla from Mackay, Idaho, the indices of refraction of which 

 are n y = 1 . 57 and n a = 1 . 46. 



OTHER POSSIBLE VALID AMORPHOUS MINERAL SPECIES 



The twenty-three amorphous minerals described in this paper 

 are all believed to be well-established mineral species. Practically 

 all of them are known from several localities and some of them are 

 very common and widely distributed minerals. Although their 

 properties vary somewhat, these minerals are fairly definite and can 

 be recognized by careful work. 



There are, however, as many more amorphous minerals which 

 have been described or named, and some of these it may be possible 

 to establish by study of suitable material. I have attempted to 

 enumerate here some of the probable amorphous minerals. 



Metastibnite, amorphous SbiS 3 . 



Jordisite, colloidal MoS 2 . 



Patronite, vanadium sulfid. 



Ostwaldite (Buttermilcherz) , colloidal AgCl. 



Ehrenwerthite, colloidal Fe 2 3 'H 2 0. 



Amorphous equivalent of fischerite. 



Schadeite, amorphous equivalent of plumbogumnite. 



Palmerite, hydrous aluminum potassium phosphate. 



Yukonite, hydrous calcium iron arsenate. 



1 Min. and Sci. Press, CXII (1916), 898. 



2 Jour. Wash. Acad. Sci., IV (1914), 181. 



