128 



with an adamantine lustre, which, after long exposure, appears 

 resinous. Hardness, 5 to 5 '5. Brittle, Infusible, and on 

 charcoal |:?er se yields only a' faint sublimate. With soda on 

 charcoal easily reduced to metallic antimony, the tantalic acid 

 forming a fusible slag with the soda. 



An analysis of the specifically lighter portion is being made, 

 and I anticipate that this will contain a larger proportion of 

 niobic acid, if indeed it should not prove to be principally a 

 niobate."^ 



I propose the name of " Stibiotantalite " for this new mineral- 

 species, which is expressive of its chemical composition. 



* The analysis of the second sample has been completed, and the lighter 

 specific gravity found to be caused by an intermixture of impurities, prin- 

 cipally silica ; the relative quantities of tantalic and niobic acids and oxide 

 of antimony being approximately the same as in the foregoing analysis. — 

 G. A. G., April 24, 1893. 



