ORES AND VEIX MATERIALS. 



607 



1 and 2 (especially the latter) show that the chief constituent in these cases is probably 

 jarosite, K 2 SO4+(Fe 2 )S3O 12 +2H 6 (Fe 2 )O 6 . As there remains a slight excess of SO 3 and 

 Fe 2 O 3 after combining the constituents of this mineral on the basis of the alkalies 

 present, a basic ferric sulphate is to be assumed as a further constituent of the mixture. 



Analysis 3 shews little pyromorphite, much anglesite, little jarosite, and much 

 hydrated basic ferric sulphate, of which latter it is impossible to determine the formula 

 definitely, since it is not known how much ferric oxide and water maybe combined 

 with the arsenic pentoxide. 



The remaining partial analyses were made to ascertain whether or not the alkalies 

 were constant constituents of this class of products of alteration of the original vein 

 material. Qualitative tests showed that pyromorphite and auglesite were occasionally 

 present in greater amount than shown in analyses 1, 2, and 3. Arsenic pentoxide was 

 found in very considerable quantity in the material from the Silver Cord mine (7). 



TABLE XIII. Miscellaneous alteration products. 



a Consists of calcium carbonate, with a little magnesium and less manganese carbonate. 



b Specific gravity at 18J C. = 2.670. Hardness, 6. 



c Soluble in strong solution of potassium hydrate after four to five hours' digestion = 65.73 per cent. 



d Specific gravity at, lej'' C. = 2.023. Hardness 5.5. 



e Soluble in strong solution of potassium hydrate after four to five hours' digestion = 97.42. 



