This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1904 edition. Excerpt: ...valuable as zinc ores but they cannot be distilled on account of their iron and lead content. These constitute what the author correctly.calls "refractory zinc sulphides." Up to the present time we have depended largely on a combination of mechanical methods for separating the zinc sulphides from the associated minerals, thus making a salable zinc product and producing a smelting concentrate containing the gold, silver, copper and lead. The usual method of procedure has been wet crushing and concentrating, followed by drying and magnetic concentration. A high degree of success has been attained by these methods where applicable. But we have ores in which the association of the zinc and lead sulphiues is so intimate that no mere mechanical means would suffice for their successful treatment. Notable local instances may be found in the Leadville district of Colorado and the Coeur d'Alene district in Idaho, some of the finely divided and intimately mixed sulphides from the latter district having the appearance of slate. The method propesed in the present paper may be divided into six stages--crushing, roasting, extracting, filtering, plating lead, plating zinc. Fine crushing is an apparent necessity. The ore must first be well roasted and later submit itself to the solvent action of a solution of soda in order that all of the lead and zinc salts may be dissolved preparatory to depositing them electrolytically. The roast may be considered the critical point in the process, and success or failure will depend upon a good roast. The result of experience shows that it is better to roast as much of the ore as possible to oxide and leave the remaining sulphur as sulphide rather than sulphate. The extraction of the zinc and lead is...