SPEISS. 



721 



The powder of the vesicular speiss was riot analyzed, as bus beeu stated before, 

 but it is probable tbat its composition and formula are the same as that of the preced 

 ing, since both are saturated speiss and contain an excess of uou combined iron. 

 However, both cannot be considered as mere mixtures of definite arseuio-sulphu- 

 rets of iron and iron, for both the iron and the arsenio-sulphuret are crystalline, and 

 they are in all probability crystallographic compounds. 1 It has been seen that slags 

 were similarly crystallographic compounds. It will be seen that mattes also are crys- 

 tallographic compounds. A few remarks will be made with regard to slag-mattes, which 

 form the highest expression of this class of substances, so that in almost every stage 

 of the smelting operations crystallographic compounds are the regular products of the 

 blast furnaces. 



The speisses analyzed are remarkable on account of 



1. The presence of antimony in such very small quantities, whilst it exists in the 

 smelting charges, aud is formed in no inconsiderable quantity in the bullion, the 

 fumes, etc. 



li. The presence of molybdenum in each and sensibly in the same amount, show- 

 ing how widely aud evenly distributed this metal is in the camp. In the writer's 

 opinion it is the first time molybdenum has beeu pointed out in speiss. It is so thor- 

 oughly concentrated in this product that it was not possible to detect it in eithei 

 bullion, slag, or fumes. 



3. The total absence of cobalt, which, as has been observed, is concentrated in 

 the skimmings of the lead of the siphon-tap, and thus thoroughly separated from 

 nickel, which, as the preceding analyses show, remains in the speiss. 



Assays of speiss for gold and silver in order to complete the study of the Leadville 

 speiss, the following assays were made of speiss belonging to the three different types 



in the Survey laboratory : 



TABLE XIII. Angays of u 



1 Exactly what Mr. Gnyard means by the term crystaJIoyraphic compounds 1 am not able to state. 

 (S. F. E.) 



MON XII- 



-46 



