The pegmatites in Evje and Iveland are home for several rare minerals. The area hosts the type localities for thortveitite, davidite-Ce, tombarthite-Y, and also good crystals of rare earth minerals, such as gadolinite-Y, euxenite-Y, monazite-Ce and others.

One of these pegmatite quarries are the Slobrekka quarry. This quarry has been worked for feldspar in periods since early twentieth century. Nowadays, it is not economical viable to produce feldspar from these small occurances anymore. It is therefore very satisfactory that the landowner has not only allowed mineral collectors into the quarry, but also blasts in regular intervals. Since 2002 good specimens of gadolinite-Y og aeschynite-Y have been found. In addition, several other minerals, such as magnetite, spessartine, albite, muscovite, bismuthinite, allanite-ce, fergusonite-Y, monazite-Ce and others has ended up in different collections.

Geology

The pegmatite field in Evje and Iveland lies somewhat 50 km north of Kristiansand. The pegmatites lies within an approximately 35km long and 10 km wide amphibolite body, located south of Evje centre and west of the river Otra.

The methamorphic rocks in this area, including the amphibolite, belong to the Telemark suite of rocks. They are formed during the precambrian sweco-norwegian orogeny that took place some 1200 mill. years ago Towards the end of the orogeny, a granitic pluton intruded the Evje/Iveland area.. Except for some outcrops north of the amphibolite, this granite is hidden underground. It’s only visible parts are all the pegmatites.

The Slobrekka pegmatite lies in the northernly part of the Iveland municipaly, at Frigstad. Slobrekka seems to be a part of a larger pegmatite complex also including Li, Litjorn, and Tuftan pegmatites. Here, the pegmatites are visible in the landscape as forested hills, whereas further south they are more frequently covered by quarternary sediments.

Bjørlykke described 106 pegmatites in Evje/Iveland in 1935, and in many ways this is still the reference work for the area. Even the locations described on Mindat.org are using this old paper as the main source of information on the localities. Even though Bjørlykkes paper is of great value, having such an old reference work may be somewhat problematic. Many of the pegmatites Bjørlykke described are lost, several new are opened after his time, and the local mining community has used a different naming convention than Bjørlykke.

The Evje/Iveland pegmatites

The pegmatites in the Evje/Iveland complex are feldspar, quartz and mica pegmatites formed by mobile restfluids from the underlaying granite pluton.

Bjørlykke (1935) and Frigstad (1968) has mapped and categorized the pegmatites in different types. Bjørlykke categorized the pegmatites into 4 different types base don the accessory minerals, but Frigstad shows that the occurance of accessory minerals are much more complex, and that Bjørlykke’s categorization is not valid. It is more convenient to separate between regular pegmatites and clevelandite pegmatites.

a) Mikroclin/quartz pegmatites

These pegmatites consists mainly of pertittic microklin (pink,red,whitish), plagioclase (greyish white to yellowish), quartz (colorless, white, smokey to black) and mica (muscovite and biotite). The most common accessory minerals are manganese rich garnet (normally spessartine > almandine) and beryl. The pegmatites can be enriched in REE minerals as well.

b) Clevelandite pegmatites

The main minerals in this type of pegmatites are albite var. clevelandite and quartz. The accessory minerals here are different than for the main type. The cleveandite type are younger than the primary pegmatites and has a pneumalittic/hydrotherrmal origin, and it is found as irregular bodies or lenses within the main pegmatite.

Some of the pegmatitic masses can be quite big, possibly in the km3 size. The gangues and lenses with larger crystallization are however smaller.The biggest pegmatite lenses are around 100m long and no more than a few tens of metres wide. There are nogeneral rules for zoning or sequence of crystallization that is common for the pegmatites, but most of the pegmatites have a graphic granite as an outer zone towards the amphibolite rock, and an inner zone of corse crystals of feldspar and mica.

Bjørlykke describes a single crystallin mass of microclin exceeding 10m length and 200 metric tons weight. Old miners can tell that this was not unique. Biotite books close to 7m has been recorded, and mica books on 2-3m are not uncommon.

Just as for the main minerals, the accessory minerals can also reach considerable size.

The history of gadolinite-Y from Slobrekka

In times with high prices for yttrium, gadolinite was in fact a mining produce, but quite often gadolinite crystals ended up in the quarry dump. Therefore it is still possible to find good collector specimens in the dumps. New blasting increases these opportunities.

In 1896, the Setesdal railroad opened, thus connecting the Evje/Iveland interior with Kristiansand on the coast. That reduced logistics cost to a level that made feldspar export to the European china manufacturers viable, and several pegmatites were opened shortly after.

It did not take long until the occurance of rare minerals became appearant, and Brøgger was there in 1906, describing 10 small feldspar quarries on the Frikstad farm. This number had increased to 11 by 1935 when Bjørlukke did his major paper on these pegmatite. Slobrekka corresponds to Bjørlykke’s Frikstad 7. He describes Slobrekka as a large pegmatite gangue with giant feldspar crystals running in an east-west direction. Feldspar was at that time produced from two different places. He also claims that Slobrekka as one of the pegmatites with the highest content of black accessory minerals.

Schetelig (in Brøgger et. al 1922) is the first that describes gadolinite from northern Iveland: ” In the northernly part of Iveland municipaly is gadolinite a quite common mineral in the granittic pegmatites, and may occure in so large masses that some of the pegmatites partly are mined for gadolinite. As an example can be mentioned that in one quarry at Frikstad, 600 kg gadolinite had been mined through the winter of 1906. I myself have seen 120kg gadolinite in one shot from another quarry at Frikstad” Whether one of these quarries where Slobrekka is not told.

Scheletig does also provide a detailed description of the gadolinite crystal development. He describes the material as “ deep greenish black, with strong resinous lustre, and the crystals as anisitrope and without pleochlorism in thin sections”



In total, Schetelig assumes that “several thousand kgs” of gadolinite had been produced from the pegmatites at Frikstad. Bjørlykke (1935) calculates the total gadolinite production from Slobrekka alone to be around 2 tons in the period up to 1935. In the period after WW2, metal prices were high and the production of gadolinite continued into the 1960-ties. There are no official record of the amounts, but Øyna et al, 2008 describes several finds of single crystals and shipments of gadolinite in the multiple 100kg range. There should be no doubt that the postwar production also could be measured in tons. Bjørlykke calculated in 1937 that the Slobrekka pegmatite contained approx. 0,013 wt% gadolinite. This may not seem like a lot, but it does imply that on average, every cubic metre of pegmatite contained the equivalent of one 6*4*3,5 cm crystal.

The largest single crystal found in Slobrekka exceeded 500kgs, and stood up in the pegmatite as a “squatting man” according to Osmund Jensen Frigstad, the miner finding the crystal. Several crystals in the 200kg range are described from both Slobrekka and nearby mines in the Frikstad and Birkeland area.

Bjørlykke describes several small, well developed and shiny black crystals in the 5-10cm range. Neumann (1985) reports a somewhat special crystal found by Orest Landsverk and investigated by A.O. Larsen and A Åsheim. This particular crystal is 1,5x3cm, and has a 1mm thick transparant green outer layer, and conventional black gadolinite core. The outer layer is crystalline, and is a mineral in the gadolinite family, whereas the core is metamict.:

Minerals

Slobrekka is a pegmatite with a relatively high content of REE elements, resulting in several quite rare minerals can be found in addition to the conventional minerals quartz, feldspar and mica. The most common accessory minerals are garnet, allanite-Ce, magnetite and gadolinite-Y. Schetelig described “priorite”, polykras, topaz and blue apatite. Topaz and blue apatite are to my knowledge not found in modern time, and in particular topaz are a bit odd, since it normally are found with cleavelandite. Bjørlykke added euxenite, ”alvite”, monazite and ”blomstrandine”. Alvite are now considered a zirkon, whereas aeschynitt-Y now covers both ”priorite” and ”blomstrandin” despite distinct differences in chemistry and appearance between the two.

Later, several other minerals has been added to the list, including thortveitite, davidite, fergusonite-Y, ilmenite and others.

Gadolinite-Y































































After the opening of Slobrekka for mineral collectors in 2003, several gadolinite-Y crystals has been found. Many of them around 2-3 cm, but some really outstanding crystals reaching almost 10 cm has been found. The gadolinites are found in different mineral assemblages. It has been found as embedded crystals in both microcline and plagioclase, but also with muscovite, and sometimes also with garnet or allanite-Ce. The crystals found in mica are often more irregular than the ones found in feldspar, which can be really nice. Also loose crystals has been found in the dumps.

Some of the gadolinites have secondary minerals on the crystal surface. Both Tengerite-Y and kamphaugite-Y has been identified.

It is often difficult to distinguish gadolinite from garnet and quartz, since both these minerals can occure in flattened, almost black crystals.

Microcline

Microcline is one of the main consituent in the pegmatite, and was together with quartz and gadolinite providing the economical basis for the mining operations. Well developed pink crystals can still be found embedded in quartz.

Quartz

Massive quartz is one of the main minerals in the pegmatite. The color ranges from clear through white to smokey quartz. The quartz here are very pure, and investigations are being performed even today to see if sufficient quantity can be produced to produce superclean quartz for producing silica for solar panels.

Plagioclase

Some of the massive plagiclase in Slobrekka are adularescent, and some pieces have successfully been cut as moonstone cabochons. Albite crystals are found together with muscovite and hematite on the dumps. The albite crystals can be up to 5 cm.























Biotite

Large biotite books are relatively common, sometimes even in pseudohexagonal shapes. Aeschynite-Y often occur with the biotite, but there are no appearant ties between biotite and gadolinite.

































Muscovite






















Muscovite are often found in sharp pseudohexagonal crystals. Crystals and crystal groups up to 10cm can be found embedded in microcline. Well developed muscovite crystals up to 4 cm can be found on albite with hematite. These crystals have only been found in the dump, but all specimens found appears to have come from the same vug.









Magnetite



Magnetite occurs as octahedral crystals or crystalline masses in feldspar or graphic granite. Magnetite is a common accessory mineral at Slobrekka, but it is difficult to free complete crystals. It seems as if magnetite and gadolinite does not occur together. Small idiomorphic crystals of euxenite-Y can be found as inclusions in the magnetite.

























Garnet

Dark red, almost black garnets is quite common, and are often found in flattened irregular crystals. Their size may be up to 6 cm. The garnet composition lies between almandine and spessartine, slightly leaning towards spessartine. The dark, almost black color is caused by a small ontent of Y2O3.

Some small (~5mm) well developed crystals of a lighter color has been found in massive epidote.

Allanitt-Ce








































Allanitt-Ce is quite common in Slobrekka and can be found in longs lender crystals exeeding 50cm in length. The crystals normally occurs in microcline that shows the characteristic radioactive alteration around the allanite crystals. The allanite is frequently altered to secondary minerals, and at least ancylite-Ce is identified as an alteration product.



Aeschynitt-Y




































Aeschynitt-Y can be found as well developed crystals in the Slobrekka quarry. The crystals are found either as loose crystals, or with reddish microcline and biotite. The crystals often grow perpendicular to the biotite cleavage plane. The crystals found recently is remarkably similar both in shape and size compared to the original descrption Bjørlykke made in 1935.





Ilmenite


Thin plates and small crystals of ilmenite has been found in several instanses. The mineral is rarer here than in many other pegmatites in the area, and does not seem to be a guide to rarer minerals as it frequently does.




































Bismuthinite


To my knowledge, only one find of bismuthinite has been made here, but to compensate for this, the single specimen was a 22cm long crystalline mass with yellow surface alteration. The surface alteration has not been analysed, but Bismutite has been identified as an alteration product of bismuthinite in other pegmatites at Frikstad, and is the likely candidate also here.























Fergusonite-Y


Fergusonite-Y has been found in small crystals to 1 cm in feldspar.Fergusonite often occurs near biotite sheets in the pegmatite.






















Polykras-Y

Several specimens with polykras-Y has been found. The crystals rarely exceeds 5 mm.



This is not a complete list of minerals from this quarry, and it is a difficult or near impossible task to establish one. For many minerals only few specimens has been found. It is likely that other minerals are present in collections that I have not access to. Also recent work in the quarry has exposed sign of hydrothermal activity, and small fluorites amognst other has been identified. It is likely that the number of minerals described from Slobrekka will increase in the coming years. A greenish gray mineral resembling thortveitie has been found recently in a several cm tall crystalline mass. Thortveitehas been found in this quarry before, vut the ID of this find has not been verified.


Sources

BARTH T.F.W (1947) The nickeliferous Iveland-Evje amphibolite and its relations, Norges geologiske undersøkelser 168a

BJØRLYKKE H (1934) The mineral paragenesis and classification of the granite pegmatites in Iveland, Setesdal Southern Norway, Norges Geologiske Tidskrift 14

BRØGGER W.C(1906) Die Mineralien der sudnorwegische Granitpegmatitgange 1, Niobate, Tantalate. Titanate und Titanniobate, Vid. Selsk. Skr. Mat-Nat Kl 1906 6

BRØGGER WC, VOGT Th, SCHETELIG I (1922): Die Mineralien der sudnorwegische Granitpegmatitgange II , Die Silikate der Seltener Erden, Vid. Selsk. Skr. Mat-Nat Kl 1922

FRIGSTAD O.F (1968) : En undersøkelse av Cleavelanditsonerte pegmatittganger i Iveland-Evje. Hovedfagsoppgave, Universitetet på Blindern

NEUMANN H (1985): Norges mineraler, NGU skrifter 68

NORDRUM F.St (2003): Nyfunn av mineraler i Norge 2002-2003, Kongsberg Mineralsymposium 2003

ØINA S (ed)(2008): Ivelend 5, gruvedrift

A special thanks to Frank Strømmen, Arild Omestad and Iveland kommune for giving me free access to their collections. Also a special thanks to the landowner for allowing mineral collectors in this fascinating pegmatite quarry.

---

In order to leave comments to this article, you must be registered