368 PROCEEDINGS OF THE ACADEMY OF 



After cleducting the quartz and calculating the remainder to 

 percentage, I obtain for the pure substance : 



Bb . . . 47.09 per cent. Oxygen . . .11.77 

 Pe , . . 3r).3fi " "... lO.GO 



S . . . 1G.94 " "... ir,.05 



The equivalent oxygen ratio of b : Po : II is as 1.1 : 1 : 1.4, or 

 nearly as 1 : 1 : H, for which I propose the formula 2(Bb + Ve) -f 311. 



The mineral described is therefore a hydrous antimoniate of 

 iron. 



In regard to the Stibnite, from which the Stihiaferrite was pro- 

 bably derived, I have to state a few facts. I made an analysis of 

 it in order to ascertain wlietlier it contained an}' antimonic acid, 

 or a large amount of iron in any form, but both questions were 

 answered in the negative. The principal difference in the compo- 

 sition of the Stibnite is the large amount of silica with which it 

 is intimately mixed, liesides a little arsenic and lead, probably 

 present as sulphurets. The quantitative determination of the 

 latter two I omitted. In all, I ascertained that the antimon}^ Avas 



fully saturated with sulphur to form the tersulphuret of antimony. 



Ill 



(Sb). The following is the result of my analysis: 



Sb 41.21 per cent. 



S 14.8o " 



Pe 02 



Si 43.34 



(1 



99.42 " 



T have also a specimen of the rock in which the A^ein of the 

 Stibnite occurs, and into which the Stibiafen'ite ramifies. The 

 l)urest part is white, some is grajisb and yellow, caused by the 

 Slibiaferrite. The fracture is rough, uneven, on some parts angu- 

 lar. I observed cracks in all directions, but, when closely examined 

 with tiie lens, I noticed that they are filled with the Stihiaferrite. 



The rock is perfectly dull, and so is the streak. 



The hardness varies between 3 and 5. 



The sjiecific gravity I found to be = 2.7529. 



Pyrochemical test : On charcoal alone no change. With carb. 

 soda, evolution of carbonic acid gas takes place; and the sub- 

 stance dissolves in the soda, forming a dirty green glass. 



In the glass tube closed on one end it affords water and dark- 

 ness. 



Hydrochloric acid has but little effect on it ; the acid solution 

 contained but a small amount of Sb and Fe. Hydrofluoric acid 

 dissolves it readily on warming, leaving but a little residue after 

 evaporating the liquor. Caustic potassa dissolves it nearl}'- all, 

 the residue left was very little. The qualitative analysis of a very 

 white piece of this rock furnished the result that the principal 

 substance is amorphous silica, mixed with a little of the oxides of 

 antimony, lead, and iron. 



