BOOK IX. 



407 



third smelter, as I have said, adds to the tertiary cakes when he re-smelts 

 them, while from the " final " cakes, thrice roasted and re-smelted, is made 

 black copper*^. 



The rudis copper from which pure copper is made, if it contains little 

 silver or if it does not easily melt, is first smelted in the third furnace of which 

 the tap-hole is always open ; and from this are made cakes, which after 

 being seven times roasted are re-smelted, and from these copper is melted 

 out ; the cakes of copper are carried to a furnace of another kind, in which 

 they are melted for the third time, in order that in the copper " bottoms " 

 there may be more silver, while in the " tops " there may be less, which 

 process is explained in Book XI. 



*'The method of this paragraph involves two main objectives — first, the gradual 

 enrichment of matte to blister copper ; and, second, the creation of large cakes of copper- 

 lead-silver alloy of suitable size and ratio of metals for liquation. This latter process is 

 described in detail in Book XI. The following groupings show the circuit of the various 

 products, the " lbs." being Roman librae : — 



ist 



2nd 



3rd 



4th 



5th 



6th 



Charge. 

 /Crude ore 

 Lead slags . . 

 ) Schist 

 I Flux 



I Concentrates from 

 slags & accretions 



/Primary matte (i) 

 Hearth-lead & litharge 

 Lead ore 

 J Rich hard cakes (A .)) 

 ' Liquated cakes 

 Slags (B) 



Concentrates from 

 accretions 



5,400 lbs. 

 3 cartloads 

 I cartload 

 20 lbs. 



Small quantity 



1,800 lbs. 

 1,200 „ 



300 „ 



500 „ 



200 ,. 



Products. 

 Primary matte (i) . . 600 lbs. 



Silver-copper alloy (A) 50 ,, 



Slags (B) 



Secondary matte (2) 1,800 lbs. 



Secondary matte (2) 



Hearth-lead & litharge 



Lead ore 

 ■^Rich hard cakes (A 4) 



Slags (B 2) 



Concentrates from 

 \ accretions 



Tertiary matte (3) . . 

 Poor hard cakes (A 5) 

 Slags (B3) 

 Concentrates from 

 accretions 



( Roasted quartz 



\ Matte (4) (three times 



[ roasted) 



1,800 lbs. 



1,200 „ 

 300 „ 

 500 „ 



II cartloads 

 3 



Silver-copper-lead 

 alloy (liquation 

 cakes) (A 2) 



Slags (B 2) . . 



Tertiary matte (3) 

 Silver-copper-lead 

 alloy (liquation 

 cakes) (A 3) 

 Slags (B 3) 



1,200 



1,300 lbs. 



1,100 



II cartloads 



Quaternary hard cakes 



matte (4) . . . . 2,000 lbs. 



Rich hard cakes of 



matte (A 4) .. 1,500 ,, 



Poor hard cakes of 



matte (A 5) . . 1,500 lbs. 



Final cakes of matte (5) 



Final matte three times roasted is smelted to blister copper. 

 The following would be a rough approximation of the value of the various products : 



(2.) 

 (3-) 



(4-) 

 A. 



A2 

 A3 

 A4 



A5 



Primary matte 

 Secondary matte . . 

 Tertiary matte 

 Quaternary matte 

 Copper-silver alloy 

 Copper-silver-lead alloy 



Rich hard cakes 

 Poor hard cakes 

 Final blister copper 



158 ounces troy per short ton. 



^5 M »• »> 



60 ,, „ 



Indeterminate. 

 388 ounces Troy per short ton. 



145 .. 

 109 



9/ " *> *» 



Indeterminate. 

 12 ozs. Troy per short ton. 



