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and from 1815 to 1898, the mines have given a net yield of about
23,000,000 kroner.

The result of the great fall in the price of silver has been that
of late years the mines have given no surplus. The total output of
the Kongsberg silver-mines up to the year 1898 has been as follows:

Year	Tons of Silver	Gross Value
1624 to 1815 .........	553	88.7	million kr.
1816 - 1898 .........	345	52.8	—        »
Total, 1624 to 1898:	898	141.5	million kr.

The silver ore produced at the Kongsberg silver-mines is
sorted and treated on rollers and separators, while the finest goods
are refined on hearths.

The virgin silver is burnt fine, while the schlichs are melted
with pyrites, and after roasting and repeated melting mixed with
lead, whereupon the furnace lead is cupelled, the result being fine
silver of 998 per mille fineness.

Some mining for silver has also token place in the districts
round Kongsberg, on fields that have been left for private
exploitation; and the same has been the case at Svenningdalen in Vefsen
(Nordland), where the mines have been worked for fahlerz and
galena containing silver, with an output during the years from
1876 to 1896, representing a value of 1 ½ million kroner.

The oldest copper mines in the country are those of Røros.
These mines were started in 1646, and the most important ones
are Storvatsgrube, Kongens Grube with Arvedals Grube, and the
Muggrube. The ore is copper pyrites at the Kongens and Arvedals
mines, and in other places cupriferous iron pyrites, of which a great
quantity is exported.

The working of the Røros copper mines has of late years
been extended. There is a new electrical establishment worked by
water-power, by which the power is transferred to the mines, and
distributed for various purposes.

The copper ore that is smelted, as a rule contains rather
more than 5 % of copper; it is roasted and melted in
water-jacketed [[** sjk bindestrek]] furnaces, whereby a first matte is produced, containing
37 % of copper. By the Manhès Bessemer process this matte is
concentrated to a concentration matte, containing 78 % of copper,
and this again by the Bessemer process into Bessemer copper
(99.5 %) which is refined.

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