Strabo Geography 3.2.8

[8] Of the various riches of the aforenamed country, ¹ not the least is its wealth in metals: this every one will particularly esteem and admire. Of metals, in fact, the whole country of the Iberians is full, although it is not equally fertile and flourishing throughout, especially in those parts where the metals most abound. It is seldom that any place is blessed with both these advantages, and likewise seldom that the different kinds of metals abound in one small territory. Turdetania, however, and the surrounding districts surpass so entirely in this respect, that however you may wish, words cannot convey their excellence. Gold, silver, copper, and iron, equal in amount and of similar quality, not having been hitherto discovered in any other part of the world. ² Gold is not only dug from the mines, but likewise collected; sand containing gold being washed down by the rivers and torrents. It is frequently met with in arid districts, but here the gold is not visible to the sight, whereas in those which are overflowed the grains of gold are seen glittering. On this account they cause water to flow over the arid places in order to make the grains shine; they also dig pits, and make use of other contrivances for washing the sand, and separating the gold from it; so that at the present day more gold is procured by washing than by digging it from the mines. The Galatae affirm that the mines along the Kemmenus mountains ³ and their side of the Pyrenees are superior; but most people prefer those on this side. They say that sometimes amongst the grains of gold lumps have been found weighing half a pound, these they call paloe; they need but little refining. ⁴ They also say that in splitting open stones they find small lumps, resembling paps. And that when they have melted the gold, and purified it by means of a kind of aluminous earth, the residue left is electrum. This, which contains a mixture of silver and gold, being again subjected to the fire, the silver is separated and the gold left [pure]; for this metal is easily dissipated and fat, ⁵ and on this account gold is most easily melted by straw, the flame of which is soft, and bearing a similarity [to the gold], causes it easily to dissolve: whereas coal, besides wasting a great deal, melts it too much by reason of its vehemence, and carries it off [in vapour]. In the beds of the rivers the sand is either collected and washed in boats close by, or else a pit is dug to which the earth is carried and there washed. The furnaces for silver are constructed lofty, in order that the vapour, which is dense and pestilent, may be raised and carried off. Certain of the copper mines are called gold mines, which would seem to show that formerly gold was dug from them.