BOOK VII. 243 



Mix one part of this ore, when it has been roasted, crushed, and washed, with 

 three parts of some powder compound which melts ore, and six parts of lead. 

 Put the charge into the triangular crucible, place it in the iron hoop to which 

 the double bellows reaches, and heat first in a slow fire, and afterward 

 gradually in a fiercer fire, till it melts and flows like water. If the ore does 

 not melt, add to it a httle more of these fluxes, mixed with an equal portion 

 of yelluw htharge, and stir it with a hot iron rod until it ail melts. Then 

 take the crucible out of the hoop, shake off the button when it has cooled, 

 and when it has been cleansed, melt first in the scoritier and afterward in 

 thd cupel. Finally, rub the gold which has settled in the bottom of the cupel, 

 after it has been taken out and cooled, on the touchstone, in order to find out 

 what proportion of silver it contains. Another method is to put a centutn- 

 pondium (of the lesser weights) of gold ore into the triangular crucible, and 

 add to it a drachma (of the larger weights) of glass-galls. If it resists melting, 

 add half a drachma of roasted argol, and if even then it resists, add the 

 same quantity of roasted lees of vinegar, or lees of the aqua which separates 

 gold from silver, and the button will settle in the bottom of the crucible. 

 Melt this button again in the scorifier and a third time in the cupeL 



We determine in the following way, before it is melted in the muffle 

 furnace, whether pyrites contains gold in it or not : if, after being tliree times 

 roasted and tliree times quenched in sharp vinegar, it has not broken nor 

 changed its colour, there is gold in it. The vinegar by which it is quenched 

 should be mixed with salt that is put in it, and frequently stirred and dissolved 

 for three days. Nor is pyrites devoid of gold, when, after being roasted and 

 then rubbed on the touchstone, it colours the touchstone in the same way that 

 it coloured it when rubbed in its crude state. Nor is gold lacking in that, 

 whose concentrates from washing, when heated in the fire, easily melt, giving 

 forth httle smell and remaining bright ; such concentrates are heated in the 

 fire in a hollowed piece of charcoal covered over with another charcoaL 



We also assay gold ore without fire, but more often its sand or the con- 

 centrates which have been made by washing, or the dust gathered up by 

 some other means. A httle of it is shghtly moistened with water and heated 

 until it begins to exhale an odour, and then to one portion of ore are placed 

 two portions of quicksilver^** in a wooden dish as deep as a basin. They are 

 mixed together with a httle brine, and are then groimd with a wooden pestle 

 for the space of two hours, imtil the mixture becomes of the thickness of dough, 

 and the quicksilver can no longer be distinguished from the concentrates 

 made by the washing, nor the concentrates from the quicksilver. Warm, or 

 at least tepid, water is poured into the dish and the material is washed imtil 

 the water nms out clear. Afterward cold water is poured into the same dish, 

 and soon the quicksilver, which has absorbed all the gold, runs together 

 into a separate place away from the rest of the concentrates made by 

 washing. The quicksilver is afterward separated from the gold by means 

 of a pot covered with soft leather, or with canvas made of woven 

 threads of cotton ; the amalgam is poured into the middle of the cloth or 



**The amalgEunation of gold ores is fully discussed in note 12, p. 297. 



