The Grua Mining
District, Oppland, Norway
By Ronald Werner
|The Grua area is one
of the classic mining districts in Norway and famous for exciting
mineral occurrences. As early as in the 16-th century, iron-ores
from the Grua district were taken out and transported to a smelter
in Hakadal, 20 kilometers to the south. In later times lead- and
zinc-ores became important. Also of significance was the
exploitation of limestone, marble and granite.
|The mining in the Grua district has
left the area with many signs of this industrial activity. All
through the area you can find abandoned mines with extensive dumps,
limestone-, marble- and granite-quarries, limestone-ovens, the
remains of a cableway, an ore-washing plant and a smelter.
The ores that were taken out contributed to the local economy,
and helped to developed this area. But the ores that were taken out,
contained more than only the valuable metals. Together with the ores
exciting crystals of minerals were found. The mines near Grua have
been visited by many famous geologists because of these beautifully
Nowadays, all the mines have been abandoned, and it is very
unlikely that work in the mines will ever be taken up again. But the
remains of the mines remind us of an important era in the history of
both Grua and Norway in general. And the beautiful minerals that
have been found in the Grua district might increase our respect for
The Hadeland Bergverksmuseum, dedicated to the mines and minerals
of Grua, is a small museum, still. But thanks to the many
interesting places in the area there is much to see and to learn.
You can spend many days walking in the area, looking at all the
remains of a rich era in Grua’s history. And at the same time you
can enjoy the Norwegian woods, dig for crystals or fish in one of
the many lakes. This brochure is intended to be your guide and show
you the interesting places.
In order to understand the origin of the ores in the Grua
district, it is necessary to go back approximately 300 million years
in the history. Norway was a completely different country then. Most
of Norway was covered by kilometer thick layers of sedimentary
rocks, like limestone, shale and sandstone.
The earth was very unstable in those times. The outside of the
earth on which we live, is under-divided in a number of continental
plates. Those continental plates are continuously moving, either
away from, or towards each other.
Try to imagine the world as an orange that has been peeled, and
you try to put back the pieces on the orange. The individual pieces
of the peel -representing the continental plates of the earth-, will
not fit very smoothly back on the orange. Such is also the case with
the crust of the earth. In addition, the individual plates move in
relation to each other. For instance, two colliding plates will
create mountains. Incredible forces are at work in the crust of the
300 million years ago the continental plate on which Oslo is
situated, was put under enormous stress, and eventually fractured.
The entire Oslo area, measuring 175 x 50 km, became an isolated
piece of crust, and started to sink down between the larger pieces
surrounding it (Fig. 1). All in all, the Oslo area sank down up to 2
kilometers! Such a structure is called a “rift valley”, or “graben”.
A modern example is the enormous East African Rift Valley.
The fractures in the crust went all the way down into the earth,
where there is no longer solid rock. Here, the rock can only exist
in molten form, as magma. This magma is of course very hot, and is
under very high pressure. The fractures made it possible for the
magma to press itself up, all the way to the surface of the earth.
This process is called volcanism, and when the magma reaches the
surface of the earth, we get volcano’s! And indeed, in the Oslo area
there must once have been hundreds of volcano’s, which covered the
whole area with basalt and other volcanic rocks.
Even now, after all those millions of years, there are still
remains of volcano’s to be seen not far from Grua. Examples of
volcano’s are the Brandukampen, Ballangrudkollen, Viksbergene and
The volcanic processes went on for many millions of years, but
eventually the situation became more quiet and the volcano’s ceased
to be active. But beneath the surface of the earth there was still
magma trapped in the enormous fractures. As said above, the original
rocks in the area were limestone, shale and sandstone. The fractures
in those rocks which made it possible for the magma to reach the
surface of the earth, were completely filled up with the magma. This
means that the extremely hot magma was in contact with the
sedimentary rocks. The heat of the magma heated up the sedimentary
rocks and altered them, comparable with the way a bread is baked.
And also, the magma contained solutions of elements like iron, zinc,
lead, copper etc. which penetrated the sedimentary rocks. These
processes of heating up and the penetration of solutions in the
sedimentary rocks is called contact-metamorphosis, and is the reason
for the presence of ores in the Grua district.
- The ores were formed at considerable depth in the earth, but are
nowadays found near the surface. During the millions of years after
the forming of the ores, Norway has been exposed to erosion. And
especially during the last ice-age which lasted till 10.000 years
ago, enormous amounts of rock were removed. Therefore, we can
nowadays see rocks at the surface that were formed at depths of
- THE FORMING OF THE
The minerals which were formed in the course of the above
mentioned process of “contact-metamorphosis” have made the Grua
district famous. Specimens of andradite and “uralite” from Grua went
to museums all over the world.
The processes that created the minerals have been studied by many
famous geologists. The most famous of these was the Swiss geologist
Victor Moritz Goldschmidt, whose studies of the Oslo area
contributed greatly to a better understanding of the forming of
minerals as the result of contact-metamorphic processes. Such
knowledge was not only of great significance for the science of
geology, but finds application in many modern industrial processes
In general, contact-metamorphosis means that a specific rock is
altered due to the effects of heat. Additionally, magma often
contains gasses and fluids that easily escape out of the magma. Such
gasses and fluids can under certain circumstances react with the
neighboring rock, and cause additional changes.
Contact-metamorphosis of the sedimentary rock-types shale and
sandstone will only result in the baking of these rocks. Shale will
become a dark, black, usually very hard rock known as hornfels.
Sandstone will be altered into quartzite.
The rock-type that is most easily affected by the processes of
contact-metamorphosis is limestone, a rock composed mainly of
calcite. Depending on the exact composition of the limestone,
different processes will take place. If the limestone is very pure,
exposure to the heat will only cause a re-crystallisation of the
limestone and it will become a new rock: marble!
If, however, the limestone is impure, different processes can
take place. The limestone can contain small amounts of quartz, which
will react with the calcite and hornfels will be formed. But the
limestone can also contain all kind of reactive elements, which can
react with the gasses and fluids from the magma. The gasses and
fluids contain elements like iron, zinc, lead, copper, fluorine,
sulfur and many others. When these come into contact with the impure
limestone, many different minerals can be formed.
In the first place, the important ore-minerals will be formed:
magnetite, pyrite, galena, sphalerite, chalcopyrite etc. But
simultaneously other minerals without direct economical value are
formed: andradite- and grossular-garnet, “uralite”, scapolite,
epidote, quartz, fluorite, calcite and others.
The ores that were taken out in the Grua district contained iron,
lead, zinc and copper. Those metals were found as the following
- iron: magnetite, hematite, pyrite, pyrrhotite
- lead: galena
- zinc: sphalerite, hemimorphite
- copper: chalcopyrite
It so happens, that the minerals without economical value very
often form beautiful crystals. The early geologists understood that
the studying of those crystals gave them important information about
the way minerals are built up out of the natural elements. Such
knowledge is fundamental to our modern technology.
In the Hadeland Bergverksmuseum you will see examples of the
different rock-types found in the Grua district, the ore-minerals,
the exciting minerals and fossils. In a following chapter the most
important minerals will be described.
ATTRACTIONS NEAR GRUA
The most important attraction in the Grua area is of course the
Hadeland Bergverksmuseum. The mines and the other interesting
geological sites in the Grua district and the surrounding area’s
will be described, and on the map you will find their location. Some
of the mines are protected, and the collecting of minerals, digging
or other forms of physical change to the sites is forbidden.
------THE HADELAND BERGVERKSMUSEUM--------
The interest of geologists and mineral-collectors for the Grua
district is only one of the fundaments on which the Hadeland
Bergverksmuseum is founded. Among some local people grew a great
curiosity for the history of the area. Those people saw the remains
of the mines, and discovered that in less than a hundred years
basically all the mines, machinery and buildings had been destroyed.
After the mines were shut down, all usable materials were
removed. Nobody realised that by doing this, the local history was
almost completely erased. This group of responsable people
understood that without immediate action all would be lost for good.
The first object that was restored was the old limestone oven at
the Østhagan Landskapsvernområde. And it must have been fate, that
shortly after the restoration of the oven, large quantities of
valuable minerals were found during the construction of the Grua
tunnel in 1991/1992. These minerals deserved to be exhibited in a
The local community and a number of dedicated volunteers spent
many months restoring the Grua Jernbanestasjon, and making the place
suitable for exhibiting those minerals. And simultaneously all kind
of relicts from the mines could get a place in this museum.
The museum was officially opened in september 1993, and has been
open every weekend since. During the sommer of 1994 the museum was
opened 6 days a week. And the future of the project is brighter than
The local community has bought an old building belonging to one
of the mining-companies, and appointed this to become the new home
for the Hadeland Bergverksmuseum. This building -Bråten- is much
larger than the station, and will allow the exposition to be
expanded. It is expected that maybe already in 1997/8 the Hadeland
Bergverksmuseum can move to this new place.
And in the meantime a project to make the Nyseter mines
accessible for the public was succesfully accomplished. Since autumn
1994 many hundreds of people have been guided through the most
impressive mine in the Grua district.
The museum offers a representative collection of the rocks and
minerals found in the Grua district. In a following chapter you will
find descriptions of the minerals and the rocks. at display in the
KARLSTJERN: near lake Nedre Karlstjern there are 2 small
mines and one somewhat larger mine. The ore minerals that have been
taken out were sphalerite, galena and maybe chalcopyrite. Samples of
these minerals can still be found on the dumps.
PRØVE: this was a very small mine near the beautiful lake
Svea. The mine was once famous among collectors for superb specimens
of azurite, probably Norway’s finest. Nowadays it is difficult to
find specimens at all. Other minerals found here include malachite,
cerussite and hemimorphite. The occurrence is more unusual in
Norway, because the last ice-age has throughout the entire country
removed nearly all such zones of the ore-mineralisations.
MUTTAGRUVEN: the mine is located 20 meters after the
cattle-grid in the road to Svea, at the right side. The mine is
fenced in and practically inaccessible. The ore that was taken out
was galena. This is a protected mine.
MUTTATJERN: this mine is located 50 meters further down
the road, at the left side. In the first place you can see in a
roadcut a 30 cm broad galena-vein. A little further down the hill
there is a small pit which worked in the same vein. Also protected!
this was by far the largest and most important mine in the Grua
district. The ore that was taken out was sphalerite, a zinc ore. The
ores were discovered in 1888. Belgium, English, German and Norwegian
mining companies have intermittently operated the mines till 1927.
There are three levels of mining galleries underground, two large
open pits and a number of smaller pits. Some of the smaller pits are
actually iron-mines, and are much older than the zinc-mines. On
certain days it is possible to visit the mines, guided by someone
from the Hadeland Bergverksmuseum. The open pits behind the fences
are an impressive sight, but for reasons of security it is forbidden
to climb over the fence.
RISTIREVBERGET: this was a very small mine not far from
the Skjærpemyr mines. The ores that were found here, are galena,
chalcopyrite and pyrite.
SKJÆRPEMYR: at the Skjærpemyr there are several small
mines where zinc-, lead- and copper-ores were taken out. The
lead-ore contained some silver. The Skjærpemyr mines are the most
interesting and richest mines in the Grua district as far as the
minerals are concerned. At least 45 different minerals are found
here! The mines are protected, but picking up stones from the
surface without digging or hammering is allowed.
TYPOGRAFHJEMMET: is a small zinc-mine north-east of Grua,
situated in the middle of woods. Interesting minerals were not found
this is one of the main attractions in the Grua district. On a
fenced-in area of 0,3 km-2 you will find two limestone-ovens,
several limestone-quarries and some very old iron-mines. In
addition, the geology of Østhagan is very good visible at many
places thanks to the exploitation of limestone. The iron-mines at
Østhagan were already operated in the early 16-th century, which
makes them among the oldest in Norway. Just before entering the
Østhagan area, you will see the opening of one of the mines at the
left side of the road. A couple of years ago the mine was emptied
for water, and many interesting old things were found. On the
fenced-in area there are three more iron mines. The limestone
quarries are much younger. The exploitation of limestone was started
in 1910, and continued intermittently till 1937. The limestone was
burned in the two limestone ovens. The restoration of the ovens will
be continued in the near future, but already now it is possible to
get a good impression of how these ovens worked. The burnt limestone
was used for cement. Østhagan is also famous for it’s rich
occurrence of dark green andradite-garnet crystals. It is among the
richest occurrences of garnet in Europe. This is a protected area
and mineral collecting is not allowed.
MINES: in the period between 1880 and 1930 there were
registered about 140 “skjerps”, small exploration shafts in order to
establish if an occurrence is profitable enough to become a mine.
This means that throughout the entire Grua district there have been
numerous efforts to find ore-deposits. Only a few of these have
actually been taken into exploitation. While walking through the
forests, you might every now and then see a small hole in the
ground, and realize that people have been digging here in order to
QUARRIES: at several places along the railway between
Bjørgeseter and Grua there are small quarries were granite has been
taken out. The granite was used by the railroad company for
enforcement of walls along the tracks, by the limestone company as
the fundament of the ovens and by the local people as fundaments for
houses. At many places you can see the typical red color of the
granite along the road south of Grua.
QUARRIES: near Grua there are two marble quarries. One is
directly west of Mylla, the other is situated between Nedre- and
Øvre-Karlstjern. Somewhat outside the Grua district, a few
kilometers south-west of Gran near the Viiksbergene, there is
another marble quarry. The marble was used for building purposes.
3) OPPEN LIMESTONE
QUARRY: this quarry is situated at the road from Svea
till Kalvsjø and is still in operation. The limestone is used for
cement production and the neutralization of the water in the lakes.
at many places the sedimentary rocks in the Grua district contains
fossils. The richest occurrences are near Lunner. During the
construction of the new road in the direction of Jevnaker hundreds
of tons of limestone with Pentamerus fossils were taken out. In the
sides along the road it is still possible to see the fossils sitting
in the rock. Other fossils found here include corals and sea-lilies.
VOLCANO’S: the remains of the volcano’s as such are maybe
not a big attraction, but are mentioned for those of you with a
deeper interest for geology. The part of the volcano that still
exists, is the so-called “volcanic neck”, a tube through which the
magma traveled upwards to the surface of the earth. The rock in
these necks is much harder than the surrounding sedimentary rocks,
and was not as deeply eroded away. Therefore form the necks
prominent hills in the landscape. This phenomena can be seen also at
other places in the Oslo area.
the zinc-ores that were taken out at Nyseter were shipped down by
means of a cableway. The cableway ran from Nyseter all the way down
to the “vaskeriet” in Grua, where the ore was washed. At several
places the fundaments of the cableway can still be seen.
PLANT: the “vaskeriet” is the place where the ores from
Nyseter were washed in order to get a product that was ready for
extraction of the zinc. The purified ores were shipped to Germany.
BLYVERKET: this is a smelter located along the Sveaselva,
south of Grua. Lead-ores from Mutta- and Skjærpemyr mines were
melted in order to extract the lead. Around the smelter piles of
slags can be seen.
THE ROCKS OF THE
The rocks found in the Grua district belong to different groups of
rocks. The plutonic rocks form at great depths by crystallisation of
magma (=molten rock). The volcanic rocks are formed when magma reaches
the surface of the earth, and cools off very rapidly. The composition
of volcanic rocks corresponds with the plutonic rocks, but they are
much more fine-grained. The sedimentary rocks can be formed as the
result of two different processes. In the first place they are formed
when already existing rocks are eroded, transported away and
accumulated at a specific place. The second possibility is when
enormous quantities of small organisms with a calcareous skeleton die,
and the skeletons accumulate.
The last category of rocks are the metamorphic rocks. These include
all the rocks that are formed when the original rocks are altered due
to the influence of temperature and/or pressure. The rock-type “gneis”
which is very abundant in Norway, is the best known example. The
contact-metamorphic rocks in the Grua district also belong to this
Diabase is a
dark plutonic rock occurring as veins (“dikes”) in the sedimentary
Gabbro is a
dark rock that is found in the volcanic necks, for instance the
Brandbukampen. Because this rock crystallized underground, it is not a
volcanic, but a plutonic rock!
Granite is a
rocktype that consists feldspar and quartz in a ratio of approximately
4 to 1. The granite in the Grua area is named “Grua granite” because
it is a slightly unusual type. Grua granite has a characteristic red
color, and can be seen directly south of Grua at many places.
include a variety of different contact-metamorphic rocks, that are
formed when shales and limestones are exposed to molten rock.
(kalkstein) is a sedimentary rock consisting mainly of calcite. The
limestone in the Grua district was formed in between 500 and 300
million years. Limestone is formed at the sea-bottom through
accumulation of billions and billions of skeletons of small organisms.
Often the limestone can contain well-preserved fossils of shells or
Rhombenporphyry is a volcanic rock that occurs
as veins (“dikes”) in the Grua district. Characteristic for this rock
is that it consists of a dark, very fine-grained ground-mass with
white, pale brown, large crystals of feldspar floating in the rock.
The feldspar crystals typically have a rhombic shape.
Sandstone is a
sedimentary rock consisting mainly of sand, glued together by calcite
or other substances.
(leirskifer) is a sedimentary rock with a red, brown, dark gray or
black color. It is formed from clay at the sea-bottom from very fine
Skarn is a
contact-metamorphic rock that is formed when limestone is altered by
exposure to molten rock, and a variety of different minerals are
formed. These minerals include calcite, garnet, pyroxene, epidote,
scapolite, quartz etc.
Syenite is a
rock-type that resembles granite very much, but contains typically
less or no quartz. The red rock near Harestua is syenite and not
granite! At the Øståsen syenite forms a large massive. Syenite is for
mineral-collectors a very interesting rock, because syenite often
contains cavities with beautifully crystallized minerals.
FROM THE GRUA DISTRICT
Aegirine is a mineral from the pyroxene-group,
and is found commonly as green needles in the syenites and granites
near Harestua. During the construction of the new Riksveg 4 excellent
pieces were found.
grossular are both garnet-minerals, and are practically
indistinguishable from each other. In general, andradite is much more
common in the Grua district than grossular. Garnets form
characteristic crystals (Fig. ?), and are usually easily recognized.
The color varies from pale yellow, green, red, brown to almost black.
The largest and best andradite-crystals were found in the quarry at
Østhagan, where the dark-green crystals could reach a size up to 10
centimeters. The smaller, reddish-brown andradite crystals found at
the Skjaerpemyr are also very popular with mineral collectors.
Azurite is a
mineral that forms when copper-ores are exposed to water and air. The
crystals (Fig.?) have a beautiful azure-blue color, and azurite is
therefore easily recognized. Azurite was once plentiful at Lykkens
Prøve, and probably Norway’s finest specimens were found here. There
is little left nowadays. Azurite can also be found at the Skjaerpemyr.
Calcite is the
most common minerals in the Grua area, considering that it is the main
component of limestone and marble. However, as beautiful crystals the
mineral is much rarer. The best calcite crystals were found in the
winter of ‘91/’92 in the Grua tunnel, while the tunnel was being
constructed. Calcite is a mineral that occurs in many different types
of crystals. The crystals can be rhombohedral or scalenohedral in many
different varieties (Fig.?). The rhombohedral crystals are the most
common, and can reach a size of 20 x 30 cm. The color varies from
white, colorless, yellow, red-brown to brown. Typical for calcite is
it’s low hardness: the mineral is easily scratched with a
is the only copper-ore found in the Grua district, and of little
economical significance. In some ore-zones the metallic, golden-yellow
parts are chalcopyrite. The mineral is easily distinguished from other
similar minerals like pyrite: chalcopyrite is very soft, and can be
scratched with a pocket-knife. Green and blue stains on the rock are
often an indication for the presence of chalcopyrite.
Epidote is an
attractive green mineral, which occurs both as large masses and as
beautiful groups of crystals. Especially at Nyseter large blocks of
green epidote are found. These are sometimes used by cutters for
making cabochons. Some of Norway’s finest epidote crystals were found
at a building-site in the center of Grua. The crystals (Fig.?) have a
beautiful dark emerald green color, and grow in delicate radiating
groups. The finest specimens are in a private collection. Epidote is
not a rare mineral and occurs at many places in the Grua area.
- Feldspars are
a group of minerals with many different members. In the Grua district
are found albite, orthoclase and microcline. Albite and orthoclase
occur mainly as veins in massive epidote at Nyseter, and as
pseudomorphosis after scapolite at Nyseter and Østhagan. Together with
calcite and quartz from the Grua tunnel small crystals of albite and
orthoclase formed a crust over the calcite and quartz.
- Microcline is found
together with smoky quartz in cavities in the syenite near Harestua
and at the Østasen. The crystals have a orange-brown color and can be
max. 10 cm large.
Fluorite is a
mineral that often is found as purple, green or colorless masses and
crystals. Crystals are very rare in the Grua district, but purple
veins through the rock can be seen at several places. In the ore-zones
fluorite is seen every now and then as purples masses.
Galena is a
metallic, gray-silvery lead mineral, easily recognized because of it’s
high specific weight. Veins and masses of galena occur at many places
in the Grua district, and many of these have been exploited.
Especially near lake Muttatjern and at the Skjaerpemyr have lead ores
been taken out. The galena of Mutta contained according to Goldschmidt
(1911) approximately 0,15 % silver, which added extra value to the
lead-ores. Also the galena of the Skjærpemyr contained some silver.
Crystals of galena are very rare in the Grua district (Fig.?)
a bright, canary yellow cadmium-mineral. Most zinc-ores contain small
quantities of cadmium, which will be dissolved outof the sphalerite
when the ore is for a longer time exposed to water and air.
Gypsum is a
mineral that is formed when ore’s are exposed to water and air, and
are decomposed. Especially at Nyseter are some mine-walls covered with
millions of small, colorless, sparkling gypsum crystals. Gypsum is a
fragile mineral and it is not easy to collect specimens.
is a typical mineral in contact-metamorphic zones. The mineral is a
member of the group of pyroxene minerals. In the Grua district the
mineral is found in massive zones of densely packed fiber’s of a dark
Hematite is a
mineral consisting of iron and oxygen, and might in a few cases have
played a subordinate role as iron-ore. The other name for hematite is
“bloodstone”, because of the dark red color of powder and thin
fragments of the mineral. Hematite occurs both as metallic, dark gray
to black masses, and as small rose-like groups of thin, tabular
crystals. Especially nice crystal-groups are found at Nyseter.
is especially found at the Skjaerpemyr. Hemimorphite is a
zinc-silicate mineral, and was formed because solutions containing
silica reacted with sphalerite. The sphalerite was earlier formed
because of a contact between limestone and syenite. Later, a granite
intruded, and gave off silica-rich solutions. Hemimorphite forms
radiating aggregates of max. 3 cm. In cavities it is possible to find
clear, lineal-shaped crystals (Fig.?). Hemimorphite is also found at
is a bright white alteration product of sphalerite. At many places in
the Nyseter mines white stains of hydrozinkite indicate the presence
of sphalerite. The mineral forms because of the exposure of sphalerite
to water and air.
Magnetite is a
metallic black iron-oxide, and was an important iron-ore. Magnetite
occurs at many places in the contact-zones in large black masses. A
magnet will be attracted by magnetite present in the rock. Especially
good observable is this at Østhagan, in the left wall of the first
iron-mine left of the road. Magnetite is a heavy mineral, having a
specific weight of 5,2 kg/dm3.
Malachite is a
bright green alteration mineral of chalcopyrite, formed when this ore
is exposed to water and air. Malachite is often found together with
azurite. Fine malachite was once found at Lykkens Prove.
Pyrite is a
very common, metallic, yellow colored mineral. Pyrite occurs both
massive and as crystals, that can be either cubes, octahedrons or
pentagondodecahedrons (Fig.?). In some cases pyrite will have been
taken out as an subordinate iron-ore. In general the quantities of
pyrite were too small to be taken out as ore. In the center of Grua,
during construction work at the roadside in front of the shops, were
for a couple of years found Norway’s finest octahedral pyrite
a metallic, bronze-brown iron mineral. Another name for pyrrhotite is
“magnetkies”, an old German name, referring to the weak magnetic
properties of the mineral. As can be seen in the museum, a magnet will
sit fast on pyrrhotite. On the Nyseter the mineral is common,
especially in small quarries south-southeast of the main mining area.
In material from the Grua tunnel small tabular, 6-sided crystals have
Quartz is a
very common mineral on earth, and also common in the Grua district.
Quartz generally forms crystals that have a characteristic 6-sided
shape. The top of the crystals are 6-sided pyramids (Fig.?). The color
is white to colorless, but somewhere near Nyseter purple colored
amethyst-quartz has been found. The crystals can reach sizes up to 10
cm, but on average they are much smaller, in between 0,5 and 1 cm. In
the syenite rocks a black variety of quartz can be found: smoky
quartz. Specimens are found near Harestua, and at the Østasen in
roadcuts at the Fylkesveg, east of Roa/Gran. The crystals occur in
cavities in the syenite, together with feldspar crystals.
Scapolite is a
somewhat rarer mineral in the Grua district, but is not uncommonly
found at Nyseter as veins in massive epidote. Scapolite is also found
at Østhagan in the vicinity of the Kalkoven. The mineral occurs
characteristically as white, pale tan or pale rose crystals, that
resemble pieces of wood to a certain extent. The crystals are long
prismatic, and form aggregates in which many crystals are intergrown
(Fig.?). Such aggregates are grown in large cavities in dark-green
andradite. In most cases the scapolite has been altered to feldspar.
the most abundant ore mineral in the Grua district, and was exploited
as zinc ore. The Nyseter mine was the most important source of zinc
ore, but ore was also taken out from the Mutta mines and at the
Skjaerpemyr. Sphalerite occurs mainly as brown, massive mineral in the
contact-zones. Tetrahedral crystals (Fig.?) of sphalerite were found
in the Mutta mines, Nysaeter, and in recent times, in the Grua tunnel.
This last occurrence has yielded very good, dark-brown crystals up to
one of the more famous minerals found in the Grua district (Fig.?). It
is actually a pseudomorphosis of an amphibole mineral after a pyroxene
mineral. In other words: the crystals were formed as crystals of a
pyroxene mineral, and later the whole substance of the crystals was
replaced by an amphibole mineral. The largest and finest crystals were
found in 1902 when the Grua railroad tunnel was constructed.
Goldschmidt (1911) describes a crystal of 7 x 12 x 10 cm. The color of
“uralite” is light green. When the crystals are studied more closely,
the surface is uneven, and they seem to be built up of fiber’s.
the Skjaerpemyr it is still possible to find large pieces of “uralite”
together with reddish-brown garnet. In this material are cavities that
are filled by calcite, visible as white veins. When the calcite is
dissolved by acid, the cavities are usually lined with small but
perfect crystals of “uralite” and andradite-garnet. The largest
uralite crystal found at the Skjærpemyr measured 8 cm.
Wulfenite is a
lead-molybdenum mineral, that is rare in Norway. In the Grua district
wulfenite occurs at some places somewhat more abundantly. At the
Skjærpemyr and Lykkens Prøve honey-brown crystals (Fig.?) were found
together with malachite and azurite.
During the construction of the
new Riksveg 4 a number of very beautiful crystals were found. The
largest crystal measures 3 mm in length, and is among the largest
crystals of this mineral found in Norway.
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