Agricola, Georgius
,
De re metallica
,
1912/1950
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310
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The fine concentrates and fine tin-stone are washed again on this canvas
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strake. </
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<
s
>By this method, the canvas lasts longer because it remains fixed,
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and nearly double the work is done by one washer as quickly as can be done
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by two washers by the other method.</
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</
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<
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>The jigging sieve has recently come into use by miners. </
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<
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>The
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metalliferous material is thrown into it and sifted in a tub nearly full of water.
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</
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<
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>The sieve is shaken up and down, and by this movement all the material
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below the size of a pea passes through into the tub, and the rest remains on the
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bottom of the sieve. </
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>
<
s
>This residue is of two kinds, the metallic particles,
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which occupy the lower place, and the particles of rock and earth, which
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take the higher place, because the heavy substance always settles, and the
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light is borne upward by the force of the water. </
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>
<
s
>This light material is taken
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away with a limp, which is a thin tablet of wood almost semicircular in
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shape, three-quarters of a foot long, and half a foot wide. </
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>
<
s
>Before the
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lighter portion is taken away the contents of the sieve are generally divided
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crosswise with a limp, to enable the water to penetrate into it more quickly.
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</
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<
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>Afterward fresh material is again thrown into the sieve and shaken up and
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down, and when a great quantity of metallic particles have settled in the sieve,
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they are taken out and put into a tray close by. </
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>
<
s
>But since there fall into
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the tub with the mud, not only particles of gold or silver, but also of sand,
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pyrites,
<
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cadmia,
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"/>
galena, quartz, and other substances, and since the
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water cannot separate these from the metallic particles because they are all
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heavy, this muddy mixture is washed a second time, and the part which is
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useless is thrown away. </
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>
<
s
>To prevent the sieve passing this sand again too
<
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quickly, the washer lays small stones or gravel in the bottom of the sieve.
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</
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>
<
s
>However, if the sieve is not shaken straight up and down, but is tilted to one
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side, the small stones or broken ore move from one part to another, and the
<
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metallic material again falls into the tub, and the operation is frustrated.
<
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</
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>
<
s
>The miners of our country have made an even finer sieve, which does not
<
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fail even with unskilled washers; in washing with this sieve they have no
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need for the bottom to be strewn with small stones. </
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>
<
s
>By this method the mud
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settles in the tub with the very fine metallic particles, and the larger sizes of
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metal remain in the sieve and are covered with the valueless sand, and this
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is taken away with a limp. </
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>
<
s
>The concentrates which have been collected
<
lb
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are smelted together with other things. </
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>
<
s
>The mud mixed with the very fine
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metallic particles is washed for a third time and in the finest sieve, whose
<
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bottom is woven of hair. </
s
>
<
s
>If the ore is rich in metal, all the material which
<
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has been removed by the limp is washed on the canvas strakes, or if the ore
<
lb
/>
is poor it is thrown away.</
s
>
</
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">
<
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>I have explained the methods of washing which are used in common for
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the ores of many metals. </
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>
<
s
>I now come to another method of crushing ore,
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for I ought to speak of this before describing those methods of washing which
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are peculiar to ores of particular metals.</
s
>
</
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>
<
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="
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">
<
s
>In the year 1512, George, the illustrious Duke of Saxony
<
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type
="
sup
"/>
14
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sup
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, gave the overĀ</
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