Agricola, Georgius, De re metallica, 1912/1950

Table of figures

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              much gold or silver, are replenished again from crude pyrites alone. </s>
              <s>If
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              from this poor ore, with melted pyrites alone, material for cakes cannot
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              be made, there are added other fluxes which have not previously been
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              melted. </s>
              <s>These fluxes are, namely, lead ore, stones easily fused by fire
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              of the second order and sand made from them, limestone,
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              tophus,
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              white
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              schist, and iron stone
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              21
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              .</s>
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              <s>Although this method of smelting ores is rough and might not seem to
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              be of great use, yet it is clever and useful; for a great weight of ores, in
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              which the gold, silver, or copper are in small quantities, may be reduced into
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              a few cakes containing all the metal. </s>
              <s>If on being first melted they are too
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              crude to be suitable for the second melting, in which the lead absorbs the
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              precious metals that are in the cakes, or in which the copper is melted out of
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              them, yet they can be made suitable if they are repeatedly roasted, some­
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              times as often as seven or eight times, as I have explained in the last book.
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              <s>Smelters of this kind are so clever and expert, that in smelting they take out
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              all the gold and silver which the assayer in assaying the ores has stated to be
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              contained in them, because if during the first operation, when he makes the
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              cakes, there is a
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              drachma
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              of gold or half an
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              uncia
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              of silver lost from the ores,
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              the smelter obtains it from the slags by the second smelting. </s>
              <s>This method of
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              smelting ores is old and very common to most of those who use other methods.</s>
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              <s>Although lead ores are usually smelted in the third furnace—whose tap­
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              hole is always open,—yet not a few people melt them in special furnaces by a
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              method which I will briefly explain. </s>
              <s>The
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              Carni
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              22
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              first burn such lead ores,
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              and afterward break and crush them with large round mallets. </s>
              <s>Between
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              the two low walls of a hearth, which is inside a furnace made of and vaulted
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              with a rock that resists injury by the fire and does not burn into chalk, they
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              place green wood with a layer of dry wood on the top of it; then they throw
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              the ore on to this, and when the wood is kindled the lead drips down and
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              runs on to the underlying sloping hearth
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              23
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              . </s>
              <s>This hearth is made of pulverised
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              </s>
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