Agricola, Georgius, De re metallica, 1912/1950

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              <s>
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              again I could furnish examples of each kind of stringers rejected by the
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              common miners which have proved good, but I know this could be of little
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              or no benefit to posterity.</s>
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              <s>If the miners find no stringers or veins in the hangingwall or footwall of
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              the main vein, and if they do not find much ore, it is not worth while to
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              undertake the labour of sinking another shaft. </s>
              <s>Nor ought a shaft to be sunk
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              where a vein is divided into two or three parts, unless the indications are
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              satisfactory that those parts may be united and joined together a little later.
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              </s>
              <s>Further, it is a bad indication for a vein rich in mineral to bend and turn
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              hither and thither, for unless it goes down again into the ground vertically or
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              inclined, as it first began, it produces no more metal; and even though it
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              does go down again, it often continues barren. </s>
              <s>Stringers which in their
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              outcrops bear metals, often disappoint miners, no metal being found in depth.
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              </s>
              <s>Further, inverted seams in the rocks are counted among the bad indications.</s>
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              <s>The miners hew out the whole of solid veins when they show clear evidence
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              of being of good quality; similarly they hew out the drusy
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              4
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              veins,
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              especially if the cavities are plainly seen to have formerly borne metal, or
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              if the cavities are few and small. </s>
              <s>They do not dig barren veins through
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              which water flows, if there are no metallic particles showing; occasionally,
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              however, they dig even barren veins which are free from water, because
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              of the pyrites which is devoid of all metal, or because of a fine black soft
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              substance which is like wool. </s>
              <s>They dig stringers which are rich in metal,
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              or sometimes, for the purpose of searching for the vein, those that are devoid
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              of ore which lie near the hangingwall or footwall of the main vein. </s>
              <s>This
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              then, generally speaking, is the mode of dealing with stringers and veins.</s>
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            <p type="main">
              <s>Let us now consider the metallic material which is found in the
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              canales
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              of
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              venae profundae, venae dilatatae,
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              and
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              venae cumulatae,
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              being in all these
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              either cohesive and continuous, or scattered and dispersed among them,
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              or swelling out in bellying shapes, or found in veins or stringers which
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              originate from the main vein and ramify like branches; but these latter veins
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              and stringers are very short, for after a little space they do not appear again.
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              </s>
              <s>If we come across a small quantity of metallic material it is an indication;
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              but if a large quantity, it is not an “indication,” but the very thing for
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              which we explore the earth. </s>
              <s>As soon as a miner who searches for veins
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              discovers pure metal or minerals, or rich metallic material, or a great
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              abundance of material which is poor in metal, let him sink a shaft on the
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              spot without any delay. </s>
              <s>If the material appears more abundant or of better
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              quality on the one side, he will incline his digging in that direction.</s>
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            <p type="main">
              <s>Gold, silver, copper, and quicksilver are often found native
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              5
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              ; less
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              often iron and bismuth; almost never tin and lead. </s>
              <s>Nevertheless tin-stone
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              is not far removed from the pure white tin which is melted out of them, and
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              galena, from which lead is obtained, differs little from that metal itself.</s>
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              <s>Now we may classify gold ores. </s>
              <s>Next after native gold, we come to the
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              </s>
            </p>
          </chap>
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