644 



GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



friable masses, composed of indistinct aud exceedingly small crystals, with a uniform 

 grayish tinge. The specimen analyzed was found at Grant sinelter, where a large 

 quantity of it is used. 



ANALYSES X, XI, AND XII. DOLOMITES. 

 Elementary. 



national. 



Discussion. The dolomites used in smelting are true dolomites, in which small 

 quantities of carbonate of lime and magnesia are replaced by carbonates of manganese 

 aud iron. The presence of chlorides was at first puzzling, for the reason that about 

 half the total quantity of chloride was soluble in boiling water when the dolomites 



