Full resolution (JPEG) - On this page / på denna sida - Second part - IX. Mining Industry and Metal Production - 1. The Iron Mines (together with information regarding other mines). By the late Prof. O. G. Nordenström - Technics of mining
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704- ix. mining industry and metal production op sweden.
The influx of water into the former is also much greater than into the latter.
In some mines it amounts to 40 or 50 hectoliters per minute. The volume of
coal, etc., hoisted per shaft is also much greater than in the ore-mines. The
shafts are everywhere perpendicular, and at the most 100 meters deep.
Picking, cobbing, and washing. At our iron-mines, the separation of
the ore from the waste is in many places done in one operation, or simply br
hand-picking. If, on the contrary, the ores are much mixed with deads of
different kinds, the separation is done in several operations, partly by hand and
partly by the aid of machinery. For magnetic iron ores it is customary to nse
magnetic separators, namely, for coarse ore, WenstrOm’s and Forsgren’s, and for
finely pulverized ore, principally GrOndal’s and Forsgren’s. The largest magnetic
separating works are at Grängesberg, Blötberget, Bredsjö and Herräng. At
Bredsjö and Herräng there are also briquette-furnaces, of the Gröndal system, in which
the finely pulverized ore is made into briquettes suitable for smelting-furnaces.
For non-magnetic iron ores wet enriching methods (washing) are used in several
places, such as Åsboberg at Striberg, Långban etc.
In zinc, lead, and silver mines, washing is common. The largest of these
works are those at the Åmmeberg zinc mines. Next in order come the washeriea
at the Kafveltorp, Stollberg, Ryllshytte and Rävåla zinc mines, the Sala lead and
silver mines, etc.
In the coal-mines the sorting of the coal from the deads (schist and
sandstone, etc.) is done down in the mines. The same is the case with the fire-proof
clay, which is excavated together with the coal.
Surveying of mines. Surveying with the theodolite is, as a rule, not very
common. This method is principally resorted to at the larger ore-fields, and only
for surveying a larger or smaller number of fixed points on the surface or down
in the mine. For further detail-surveying between these fixed points, the Swedish
surveying method (Scenska Markscheidermetoden) is used.
This method of surveying, which is neither known nor used in any other
country, has here been in use for 270 years, and has always given very
satisfactory results. The surveying-results may be considered especially good, since,
during the last 30 years, a number of improvements have been made in the
surveying-instruments, and since steel measuring-tape has begun to be used in all
more important length-measurements. This method is also much more convenient
than surveying with theodolite, especially with the configuration which the working
chambers in our mines generally have.
According to the regulations of the Swedish Mining Act of May 16, 1884,
all plans and sections of ore-mines must be drawn on a scale of 1 : 800, and
must be made in conformity with a Normal Map, drawn up by the Mining
Department («Bergsöfverstyrelsen»). Consequently all shafts and other excavations
must be shown on the plans. Further, both the parts of the excavation where ore
of different kinds occur, and those occupied by the country, gangues, dykes, etc., must
be distinctly marked with certain specified colours. Contrary to the rule in other
countries, it is decreed that no more than one horizontal section may be drawn
on each sheet, and this rule has been followed in Sweden ever since mine plans
first began to be drawn up, 270 years ago, or in 1629.
The mine plans made in this way give a very clear and exact idea, not only
of the configuration of the excavation, but also of the mode of occurrence of the
ores contained in the mine, and, for that matter, everything pertaining to the
geological conditions of the mine.
According to the Mining Act, it is also decreed that all mine plans must be
drawn in duplicates. One of these copies is to be kept at the mine, and to be
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