New mineral discoveries from the Larvik PlutonicComplex, southern Norway
Tomas Husdal1, Fabrice Dal Bo1, Henrik Friis1, Svein-Arne Berge2,Ole-Torstein Ljøstad3 and Peter Andresen41Natural History Museum, University of Oslo, PO Box 1172 Blindern, N-0318 Oslo, Norway
Hegnaveien 57, N-3235 Sandefjord, Norway
3
Elgveien 30, N-2406 Elverum, Norway
4
Solumgata 7, N-3733 Skien, Norway
2

Introduction
The Larvik Plutonic Complex (LPC) in Norway comprises a series of plutons mainly of monzonitic
composition, formed during Permian rifting in the Oslo area in southern Norway. The monzonites hosta large number of syenitic pegmatites known for their mineral diversity and in particular the many Beminerals (Larsen 2010). The most recent list has 226 unique mineral species including 26 Be- minerals(Larsen 2018). We here present seven additional species including trimerite, the 27 th Be-mineral fromthe area, as well as chabazite-Na, chernovite-(Y), desclozite, ferriallanite-(Ce), segnitite andvanadinite.
Data were collected at NHM in Oslo and is stored on their computers and can be sent on request.
“Pow_...” refers to X-ray powder patterns collected with the Gandolfi method on the single crystal
diffractometer. EDS spectra were collected on unpolished material using SEM, and quantified without
external standards. The analysed sample of chabazite-Na is in the collection of TH (sample number S6.53); the three TH/SAB micromounts are in the collection of SAB.

Trimerite, CaMn2+2Be3(SiO4)3
Trimerite was found in a single micromount specimen (sample TH/SAB 20), collected by SAB in thelarge pegmatite in the Saga I quarry, Mørje, Porsgrunn, in June 1982. It forms massive aggregates ofpale yellowish brown plates covering an area of almost 1 x 1 cm in a porous matrix between crystalsof analcime (Figs. 1a,b). Individual plates are up to 1 mm in largest dimension and display no external
crystal forms. Associated and younger minerals are bertrandite, natrolite and some unidentified, blackand white, powdery phases.
Trimerite was identified by EDS (T-38 9) giving (at.%): Si 11.5, Mn 7.6, Ca 3.36, Sr 1.21, Na 0.71. Its
XRD pattern (Pow_285) is in good agreement with PDF 00-017-0477 (trimerite). Single-crystal datawere collected from a small fragment using CuKα radiation and refined to R1 = 5.6% in the monoclinic
space group P21/n with a = 8.1033(1) Å, b = 7.6383(1) Å, c = 14.0761(1) Å and β = 90.002(1)°. The
refinement of the Ca site occupancy indicates a mixed occupancy between Ca, Sr and Na resulting in asite occupancy of (Ca0.6Sr0.3Na0.1). The Saga I pegmatite is the first locality of trimerite outside theFilipstad area, Sweden, and the material from Saga differs from the Swedish material in having asignificant amount of Sr and Na replacing Ca, giving slightly larger unit- cell dimensions.

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Fig. 1a (left). The sample “TH/SAB 20” from the Saga 1 pegmatite. FOV 10.2 mm.
Fig 1b (right). Aggregates of brownish trimerite in sample “TH/SAB 20”. FOV 3.53 mm.
Both photos: OT Ljøstad.

Chabazite-Na, (Na3K)[Al4Si8O24] · 11H2O
The late Jens Andreas Larsen made a significant find of sphaerobertrandite in the Johs Nilsen quarryon 1 June 2014. Sphaerobertrandite forms white to beige, globular aggregates up to around 0.1 mm insize on rhombohedral calcite and acicular aegirine in cavities in analcime. Chabazite-Na, discovered
by OTL, forms colourless pseudorhombohedra up to 0.03 mm in size on the surface of theseaggregates (Fig. 2a), directly on the aegirine needles (Fig. 2b) or, in rare cases, on natrolite. Other
minerals in this material are analcime, annite, a feldspar, fluorite, hambergite, and stilpnomelane. EDSof chabazite-Na (T-37 1) gives Na >> Ca > K, and an XRD powder pattern (Pow_759), althoughrather weak due to the small crystal size, is of the chabazite type. This is the first member of thechabazite group found in the LPC. Larsen made a smaller find of sphaerobertrandite in the Johs Nilsen
quarry in February 2015, here associated with aegirine, analcime, arsenopyrite, calcite, chiavennite,epididymite, a feldspar, and zircon. Chabazite-Na does not occur in this material.

Fig. 2a (left). SEM-photo of pseudorhombohedral chabazite-Na on globular sphaerobertrandite. Johs
Nilsen quarry.
Fig. 2b (right). Aggregates of colourless chabazite-Na on acicular aegirine, Johs Nilsen quarry. FOV
0.97 mm. Photo: OT Ljøstad.
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Descloizite, PbZn(VO4)(OH)
Descloizite was discovered by PA in AS Granit quarry, Tvedalen, Larvik, in 2005. The mineral forms
aggregates (0.5 mm across) consisting of platy crystals. The colour is orange yellow and theaggregates are found on a feldspar fracture surface. On the same surface, but not in direct contact withthe descloizite, is a zone rich in wulfenite. Associated with the descloizite are small fibres ofvanadinite. The identification is based on the XRD pattern (Pow_790) and EDS, which gives analmost perfect stoichiometry for descloizite. This is the first find of descloizite in Norway. The sample
is in the collection of the Natural History Museum in Oslo (k. nr. 44122).

Ferriallanite-(Ce), CaCe(Fe3+AlFe2+)[Si2O7][SiO4]O(OH)A small micromount (TH/SAB34), collected by SAB in 1990 together with a small number of
additional samples from pegmatite material at the Buer dump in Bjørkedalen, Porsgrunn, hasaggregates of dark brown to black, prismatic crystals of ferriallanite-(Ce) up to 0.3 mm in size
occurring in a cavity in microcline (Figs. 3a,b). Associated minerals in the cavity are albite,fluorapatite, two generations of zircon and a yellow helvine group mineral. Observed crystallization
sequence is albite  zircon and “helvine”  ferriallanite-(Ce)  zircon  fluorapatite. EDS (T-3827) of ferriallanite-(Ce) gives a rough composition of LREE0.7Ca1.2Fe1.7Mn0.3Al1.1Si3.0O14, with Ce
being the dominant LREE. The mineral can be classified as a manganoan ferriallanite-(Ce). The
identity was confirmed by single-crystal XRD data using MoKα radiation. The unit-cell parameters
are: a = 8.9594(7), b = 5.7729(3), c = 10.2240(8), β = 114.72(1), P21/m, Z = 2. The refinement of thecrystal structure (R1 = 4.7%) indicates the following cationic repartition: A1 = Ca, A2 = Ce0.63Ca0.37,
M1 = Fe0.62Al0.38, M2 = Al, and M3 = Fe, thus giving the ideal structural formula
CaCe(FeAlFe)[Si2O7][SiO4]O(OH). These data are in agreement with the description of ferriallanite(Ce) (Kartashov et al. 2002).

Fig. 3a (left). Dark brown crystals of ferriallanite-(Ce) with colourless prisms of fluorapatite, whitezircon and a yellow crystal of a helvine group mineral. Sample “TH/SAB 34” from Buer, Bjørkedalen,Porsgrunn. FOV 0.88 mm. Photo: OT Ljøstad.
Fig. 3b (right). SEM-photo of ferriallanite-(Ce) from Buer, Bjørkedalen. This is the same aggregate asin Fig. 3a.

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Segnitite, PbFe3+3(AsO4)(AsO3OH)(OH)6, and chernovite-(Y), Y(AsO4)
Both minerals occur intimately intergrown, associated with altered arsenopyrite in the Jahrenpegmatite at Jahrehagen cottage grounds, Stavern, Larvik, in material collected by PA. They form
crystalline crusts up to 0.5 mm2 that are white to yellowish in colour and have been identified by their
XRD patterns (Pow_811+812). Segnitite is closely related to beudantite, but the EDS analyses gave
Pb:As:Fe = 0.87:2.15:2.98 and no S, confirming the identification. This is the second Norwegian findof segnitite, after the Hellemobotn pegmatite (Husdal 2019). There are other secondary minerals
occurring on the altered arsenopyrite, but only wulfenite has so far been identified. Arsenopyrite is not
an abundant mineral in the pegmatite, and in this part it is always partly to completely altered. Otheryttrium bearing minerals in this part of the pegmatite are xenotime-(Y) and a mineral probably related
to or belonging to the rhabdophane group. These minerals are of secondary origin and related tohydrothermal alteration of the pegmatite. The primary source of yttrium is not known. Otherassociated minerals are eudidymite, epididymite, zektzerite, zircon, aenigmatite, brookite andaspedamite or an aspedamite-like mineral (Andresen et al. 2018). The analysed micromount sample isin the collection of PA.

Vanadinite, Pb5(VO4)3ClA small micromount (TH/SAB 26), collected by SAB in the Tuften quarry, Tvedalen. Larvik, in
1985/86, has a cavity with a small area of radiating aggregates of yellow needles up to 0.1 mm inlength (Fig. 4). EDS (T-35 136) gives Pb:V:Cl = 4.94:3.00:0.69 which, combined with the hexagonalcross section of the crystals, supports the conclusion that the mineral is vanadinite. This is the firstmineral with significant V found in the LPC. Associated minerals are analcime and greyish, tetragonal
bipyramids visually identified as wulfenite. Some small fragments of galena are present in the sample,
seemingly remnants of a larger crystal and most likely the source of Pb in vanadinite and wulfenite.
The pegmatites in the LPC are known for abundant molybdenite, which is believed to be the source ofMo in wulfenite. The source of V in vanadinite is uncertain. Vanadinite has also been found associatedwith descloizite from AS Granit (see descloizite description above for details). At AS Granit thevanadinite forms faint yellow fibres with a hexagonal cross section andEDS revealed approximately
10 % As substituting for V.

Fig. 4). Vanadinite with analcime
from the Tuften quarry, sample“TH/SAB 26”. FOV 0.62 mm. Photo:
OT Ljøstad.

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References
Andresen, P., Friis, H., Kjærnet, T. & Larsen, A.O. (2018): The minerals of the Jahren pegmatite, oneof the major pegmatites in the Larvik Plutonic Complex. Norsk Mineralsymposium 2018, 522.
Husdal,T. (2019): Nyfunn av mineralerMineralsymposium 2019, 31-46.

fra

Tysfjord-pegmatittene,Nordland.

Norsk

Kartashov, P.M., Ferraris, G., Ivaldi, G., Sokolova, E. & McCammon, C.A. (2002): Ferriallanite-(Ce),CaCeFe3+AlFe2+(SiO4 )(Si2O7)O(OH), a new member of the epidote group: description, X-rayand Mössbauer study. The Canadian Mineralogist 40, 1641-1648.
Larsen, A.O. (ed.) (2010): The Langesundsfjord. History, geology, pegmatites, minerals. Bode Verlag
Gmbh, Salzhemmendorf, Germany, 240 pp.
Larsen, K.E. (2018): List of minerals found in the Larvik Plutonic Complex, Mindat, accessed 26
March 2019,www.mindat.org/article.php/1747/List+of+minerals+found+in+the+Larvik+Plutonic+Complex>

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