W. T. Schaller — Mineralogical Notes. 155 



Measurements for the new prism j = {320} are as follows : 



Cryst. Size of 

 No. face. Ren. Meas. Cale. 



1 narrow p. 110 : 320 9° 39' 10° 44' 



2 broad p. 010 : 320 61 21 61 05 



2 " g. 320 : 320 57 12 57 48 



3 " f. 010 : 320 61 12 61 06 



4 " g. 010 : 320 61 13 61 06 



The faces of {133} and {100} are large, those of {163}, 

 {103}, {110}, {320}, small, while the others are usually very 

 narrow faces. 



3. Evan site from Two American Localities. 



Idaho. — Some specimens of evansite, reported as being found 

 in the immediate vicinity of Goldburg, Idaho, were received 

 through the courtesy of Mr. C. R. Potts of that place. The 

 massive, amorphous mineral occurs in seams and is very brittle, 

 with a conchoiclal fracture. The hardness is about 3, and the 

 color, while usually brown, varies considerably, becoming at 

 times colorless, also yellow or white or a dark red. The brown 

 specimens resemble common brown opal very much. 



An analysis of the brown material gave the following re- 

 sult : 



H 2 _ 36-96 Loss of water 



P 2 B 19-14 at 107° 20-00 



Fe 2 3 5-49 175 7-36 



A1 2 3 34-48 255 3'13 



CaO 4-32 290 '94 



MgO trace to low redness 390 



FeO none blasting 1/61 



100-39 36-94 



A determination, by means of Thoulet solution, of the rela- 

 tion of the density to the amount of iron present gave the 

 following values : 



Color of mineral 



Amount Fe 2 3 



Av. density 



Limits 



dark red 



6 - 60 per cent 



2-00 



1-990-2-016 



brown 



5-49 " 



1-98 



1-972-1-990 



yellow 



2-15 " 



1-94 



1-927-1-947 



By plotting these values, it is found that the density of the 

 mineral free from iron should be between 1*88 and 1*91, though 

 this value does not necessarily represent that of pure evansite, 

 as the material on which these determinations were made 

 contains appreciable calcium. Forbes* gives the following 

 determinations of the density : 



* See literature at end of paper for references. 



