106 W. P. Headden — Stannite and some of its 



seams ; but this substance which is one of the end products of 

 the alteration, an impure oxide of tin, can be traced as minute 

 threads running through the mass in every direction even into 

 its deeper portions where small portions of the original stan- 

 nite still remain. 



The meshes of this reticulation are sometimes filled with an 

 apparently homogeneous mass of a varying green color and 

 strong vitreous luster, but this is rather exceptional. The rule 

 is that they are filled with material which varies macroscopi- 

 cally and probably chemically ; as some of the patches are 

 white while others are different shades of blue or green. 



The firmer portion of the mass is really not uniform in 

 color, green and grayish black portions being intimately 

 mingled, producing a greenish black. The stannite frequently 

 shows a bronzy tarnish which makes the mixed nature of the 

 mass apparent. The luster of this mass on a fresh fracture 

 surface is metallic, its streak and powder are green and it 

 yields three products when treated with hydric chloride, i. e. a 

 solution containing a large amount of tin and a residue made 

 up of fragments of the remaining stannite and a yellowish 

 white powder consisting of stannic oxide with a trace of iron. 



The stannite is grayish black. It tarnishes blue and bronze. 

 Hardness 4 ; Sp. gr. 4 534, streak black. The material used 

 for analysis appeared to be quite pure and free from the 

 accompanying alteration products, but both the quantity of 

 the material and the size of the fragments forbade any further 

 attempt to purify it by gentle rubbing or other means. The 

 analysis yielded the following results : 



At. eq. 



Sulphur _ 28-26 88-31 



Tin 24 08 20-40 



Copper 1 29 81 47*16 



Iron 7-45 1330 



Zinc 8-71 13-40 



Cadmium 033 0*20 



Antimony . .. trace 



Insoluble . 1-51 



100-15 



If we assume the copper to be present as cuprous and the 

 tin as stannic sulphide, and express the atomic equivalents in 

 terms of sulphur, we obtain : 



Sulphur 88-31 or 6*64 6'64 1 



Tin 40-80 3-06 ) 



1-77 



Copper 23-5J 



Iron .. 13-30 l'OO , 



Zinc., 13-40 1-02 J 



Cadmium 0-20 



} 6-83 1-02 



