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Aurum, Gold

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114
AURUM.
appears to be now uniformly employed in all the mints of the Continent, and likewise of America.
The refining and assaying of gold form the natural sequence to this notice of the " standard of purity." We have already seen from Agatharcides' details how the old Egyptians refined the gold they obtained by quartz-crushing. This process, however, would only separate the baser metals, not the silver of the native alloy. How the Greeks and Romans subsequently contrived to obtain it so absolutely pure, still remains a problem. Unfortu­nately our grand authority Pliny fails us here, giving only a few incidental hints. Speaking of misy (crude arsenic), he alludes to its use in this process : " hoc admiscent qui aurum purgant." Arsenic still enters into the composition of gold-solder to make it more fusible. In another place he notes that gold was refined by melting it along with lead. Again (xxxiii. 22), he mentions the common employment of quicksilver for the same object, as the most effectual means, the pounded ore being immersed in the fluid, and shaken for a long time in an earthen pot, by which means " the gold was forced to vomit up all its impurities." To separate the quicksilver, the amalgam was put in a leather bag, when by pressure the former oozed through the pores of the leather, leaving the gold behind pure. But, in fact, this amal­gamation would not extract the silver. This is now effected by quartation, an operation taking its name from the addition of suffi­cient silver to the mass to constitute three-quarters of the weight. The mixed metal being immersed in nitric acid, the silver is attacked and dissolved into powder, the gold remaining intact in the form of a spongy mass. Mentioning its extreme infusibility, he adds that the best material for melting gold (which resisted the hottest charcoal-fire) was paleae, or straw that has been threshed—a strange fact, if correct, which he again adduces in his notice of the best materials for smelting the various metals (xxxiii. 30).
The assaying of gold was called obressa or obryza, the etymology of which has been much disputed: although in all likelihood it is a Spanish or Punic word, like all the rest connected with gold-mining, and already quoted. In our own language an ana­logy presents itself in the same department; our mining terms
Aurum, Gold Page of 453 Aurum, Gold
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