BOOK IX.

407

third smelter, as I have said, adds to the tertiary cakes when he re-smeltsthem, while from the “ final ” cakes, thrice roasted and re-smelted, is madeblack copper 46 .

The rudis copper from which pure copper is made, if it contains littlesilver or if it does not easily melt, is first smelted in the third furnace of whichthe tap-hole is always open ; and from this are made cakes, which afterbeing seven times roasted are re-smelted, and from these copper is meltedout; the cakes of copper are carried to a furnace of another kind, in whichthey 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, whichprocess is explained in Book XI.

46 The method of this paragraph involves two main objectives—first, the gradualenrichment 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 isdescribed in detail in Book XI. The following groupings show the circuit of the variousproducts, the “ lbs.” being Roman librae :—

1st

Charge.

Crude oreLead slagsSchistFlux

Concentrates fromslags & accretions

5,400 lbs.

3 cartloads1 cartload20 lbs.

Small quantity

Products.

Primary matte (1) .. 600 lbs.

Silver-copper alloy (A) 50 ,,

Slags (B)

2nd

/Primary matte (1) 1,800 lbs

Hearth-lead & litharge 1,200 ,,

Lead ore .. .. 300 „

j Rich hard cakes (A , ( ) 500 „

Liquated cakes .. 200 „

Slags (B)

Concentrates froml accretions

' Secondary matte (2) 1,800 lbs.

Silver-copper-leadalloy (liquationcakes) (A 2 ) .. 1,200 „

Slags (B 2)

3rd

I Secondary matte (2) 1,800 lbs

Hearth-lead & litharge 1,200 „Lead ore .. .. 300 „

Rich hard cakes (A 4 ) 500 ,,

Slags (B 2 )

Concentrates fromj accretions

y

/

4th

Tertiary matte (3) .. 11 cartloads

Poor hard cakes (A 5 ) 3 „

Slags (B 3)

Concentrates fromaccretions

Tertiary matte (3) 1,300 lbs.

Silver-copper-leadalloy (liquationcakes) (A 3) .. 1,100 ,,

Slags (B 3 )

Quaternary hard cakes

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

Rich hard cakes of

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

I Roasted quartz5th j Matte (4) (three times

( roasted) .. .. ix cartloads

Poor hard cakes ofmatte (A 5) .. 1,500 lbs.

Final cakes of matte (5)

6th Final matte three times roasted is smelted to blister copper.

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

(I-)

(2.)

( 3 -)

( 4 -)

A.

A2

A 3

a 4

A 5

Primary matteSecondary matte ..Tertiary matteQuaternary matteCopper-silver alloyCopper-silver-lead alloy

*> >$ t ,Rich hard cakes

Poor hard cakesFinal blister copper

158 ounces troy per short ton.

85 >> » >»

u >> ji

Indeterminate.

388 ounces Troy per short ton.

145 >> *> >>

top ,, ,, ,,

97 >> >» >>

Indeterminate.

12 ozs. Troy per short ton.