720 



GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



The sample of vesicular sjieiss was made up of equal parts of uiue specimens, 

 collected, three at the American smelter, two at the Harrisou, four at the Ohio aud 

 Missouri. 



By siltiug, it was separated iuto — 



Total 100.00 



The iron graius are also perfectlj- free from arseuic aud verj- tough. The speiss 

 powder of this sample was uot analyzed, as iu all probability its composition is the 

 same as that of type No. 2; but it was assayed for gold and silver. (See speiss assay 

 No. 5.) 



Conclusions. — The sieve examination of speiss shows: I. That speiss type No. 1 

 contains no free iron and is a non saturated speiss. 2. Tiiat speiss type No. 2 contains 

 just enough iron in excess to indicate that it is satuiated with iron. 3. Lastly, vesicu- 

 hir speiss type No. 3 contains a very large excess of free iron. It is a supersaturated 

 speiss, whose fusion has been prevented by this excess of infusible iron. 



The writer made three comparative experiments on the fusibilitj' of the three 

 kinds of speiss. In each case the pulverized speiss was mixed with borax in a porce- 

 hiin crucible, heated over the blast-lamp, properly regulated to operate as nearlj' as pos- 

 sible in the same conditions. Speiss types No. 1 aud No. 2 melted easily, and no 

 ajipreciable difference could be detected iu their melting i)oint. Speiss type No. 3 was 

 melted with more difficulty than the preceding aud formed a vesicular button, show- 

 ing iucomi)lete fusion. 



Ajjalyses XXXVII AND XXXVIII. Speiss. 



Sulphur 



Arsenic 



Autimony 



Iron 



Zinc 



Silver 



Gold 



Le.ld 



Copper 



Nickel 



Molybdenum . 

 Loss 



Total 



Silver ounces to ton . 



Gold do 



5. 8191 

 31. 4725 

 Trace 

 CO. 5780 



Faint trace 

 0. 0085 



Kaint trace 

 1. 4935 

 0. 3G28 

 0. 0876 

 0. 2110 



21. 6003 

 6. 1450 



70. 4780 

 Trace 

 0. 0301 

 0. 0009 

 2.5030 

 0. 2566 

 0. 0981 

 0. 2155 

 0. 0030 



2.48 

 Trace 



8. 7822 

 C.26 



Discussion. — The formula of the large crystalline speiss analyzed in XXXVII is 

 {FeM)cAsS, M desiguatiug the small quantities of metals accompanying iron, aud the 

 rational Ibrmula is probably represented by Fe5As(FeM)S. 



The tine-grained speiss analyzed in XXXVllI is represented by the formula 

 (FeMjgAsS, and probably l^y the rational formula Fe8As(FeM)S. 



