BOOK IX. 



401 



Because lead and copper ores and their metals have much in common 

 with silver ores, it is fitting that I should say a great deal concerning them, 

 both now and later on. Also in the same manner, pyrites are smelted separ- 

 ately if there be much of them. To three parts of roasted lead or copper 

 ore and one part of crude ore, are added concentrates if they were made by 

 washing the same ore, together with slags, and all are put in the third furnace 

 whose tap-hole is always open. Cakes are made from this charge, which, 

 when they have been quenched with water, are roasted. Of these roasted 

 cakes generally four parts are again mixed with one part of crude pyrites 

 and re-melted in the same furnace. Cakes are again made from this charge, 

 and if there is a large amount of copper in these cakes, copper is made 

 immediately after they have been roasted and re-melted ; if there is little 

 copper in the cakes they are also roasted, but they are re-smelted with a little 

 soft slag. In this method the molten lead in the forehearth absorbs the 

 silver. From the pyritic material which floats on the top of the forehearth 

 are made cakes for the third time, and from them when they have been 

 roasted and re-smelted is made copper. Similarly, three parts of roasted 

 cadmia 38 in which there is silver, are mixed with one part of crude pyrites, 

 together with slag, and this charge is smelted and cakes are made from it ; 

 these cakes having been roasted are re-smelted in the same furnace. By this 

 method the lead contained in the forehearth absorbs the silver, and the silver- 

 lead is taken to the cupellation furnace. Crude quartz and stones which 

 easily fuse in fire of the third order, together with other ores in which there 

 is a small amount of silver, ought to be mixed with crude roasted pyrites or 

 cadmia, because the roasted cakes of pyrites or cadmia cannot be 

 profitably smelted separately. In a similar manner earths which contain 

 little silver are mixed with the same ; but if pyrites and cadmia are not 

 available to the smelter, he smelts such silver ores and earths with litharge, 

 hearth-lead, slags, and stones which easily melt in the fire. The concentrates 39 

 originating from the washing of rudis silver, after first being roasted 40 until 

 they melt, are smelted with mixed litharge and hearth-lead, or else, after 

 being moistened with water, they are smelted with cakes made from pyrites 

 and cadmia. By neither of these methods do (the concentrates) fall 

 back in the furnace, or fly out of it, driven by the blast of the bellows and the 

 agitation of the fire. If the concentrates originated from galena they are 

 smelted with it after having been roasted ; and if from pyrites, then with 

 pyrites. 



Pure copper ore, whether it is its own colour or is tinged with chrysocolla 

 or azure, and copper glance, or grey or black rudis copper, is smelted in a 

 furnace of which the tap-hole is closed for a very short time, or else is always 



88 The term cadmia is used in this paragraph without the usual definition. Whether 

 it was cadmia fornacis (furnace accretions) or cadmia metallica (cobalt-arsenic-blende mixture) 

 is uncertain. We believe it to be the former. 



39 Ramentum si lotura ex argento rudi. This expression is generally used by the author 

 to indicate concentrates, but it is possible that in this sentence it means the tailings after 

 washing rich silver minerals, because the treatment of the rudis silver has been already 

 discussed above. 



*Ustum. This might be rendered " burnt." In any event, it seems that the material 

 is sintered. 



