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Article

Columbite–Tantalite from Northern Scandinavia (Kaustinen, Kolmozero) Pegmatites: An Optical and Spectroscopic Properties

by
Miłosz Huber
1,*,
Daniel Kamiński
2 and
Urszula Maciołek
2
1
Department of Geology, Soil Science and Geoinformacy, Faculty of Earth Science and Spatial Management, Maria Curie-Skłodowska University, 2d/107 Kraśnickie Rd, 20-718 Lublin, Poland
2
Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie-Sklodowska University in Lublin, 20-031 Lublin, Poland
*
Author to whom correspondence should be addressed.
Crystals 2023, 13(4), 612; https://doi.org/10.3390/cryst13040612
Submission received: 28 February 2023 / Revised: 19 March 2023 / Accepted: 21 March 2023 / Published: 3 April 2023
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals (2nd Edition))
Browse Figures
Versions Notes

Abstract

:
LCT (lithium–cesium–tantalum) pegmatites from the Kaustinen and Kolmozero regions contain columbite–tantalite mineralization, which has been presented in this study. Crystal structure, Raman microscopy, and optical property analyses of these minerals were performed. As a result of the structural studies and micro-area analyses, it was determined that these minerals in the pegmatites in question constitute a solid solution with numerous Mn-Fe and Nb-Ta substitutions within a single crystal. The ratio between Mn-Fe and Nb-Ta can change from crystal to crystal, which makes it impossible to find precise stechiometry between these ions. The crystallization conditions of these minerals were also determined by studying the associations of other rock-forming minerals and accessory minerals in the discussed rocks.

1. Introduction

In the region of northern Finland and Russia (NE Scandinavia), LCT (lithium-cesium-tantalum) pegmatites are exposed, containing lithium and columbite–tantalum mineralization [1]. In the case of Russia, this is the Kolmozero region, located in the northern part of the Kola Peninsula, where pegmatites up to several meters thick are exposed in the vicinity of Archean rocks [2,3,4,5,6,7]. In the case of Finland, it is in the Kaustinen region where such formations can be found [8,9]. These are rocks of granitoid composition, rich in quartz, plagioclase, and orthoclase, muscovite, and accessory minerals such as apatite and zircon. These minerals are accompanied by spodumene, and in its vicinity can be found several ore minerals, including grains of columbite–tantalite. These pegmatites are the product of residual crystallization under the influence of hydrothermal processes. The purpose of this article is to discuss the microscopic and spectroscopic differences between columbite–tantalite coming from these two regions.

2. Geology of the Study Area

The northern part of the Scandinavian Peninsula is part of the Baltic shield included in Fennoscandia [10,11,12,13] (Figure 1). It is a region located within Finland and Russia [14,15,16].
Archean and Proterozoic gneisses metamorphosed in amphibolite and granulite facies are exposed there [18,19]. In these rocks, there are numerous younger intrusions with interesting mineralization [20]. Veins forming pegmatites mainly of granitoid composition are exposed there. Among these veins, LCT pegmatite are also encountered, characterized by spodumene/lepidolite–columbite–tantalite mineralization [21,22]. They usually form bodies of up to several meters in thickness, located over several tens of meters. In the Kolmozero area, these veins are located in the boundary zone between the Kola and Murmansk blocks, while in the Kaustinen area they accompany Belomorides (Figure 1). Their age has been estimated at 1.8–1.9 Ga years [23,24]. These rocks are exposed on the ground surface or covered by a small overburden of Pleistocene sediments [25,26]. These formations form an interesting landscape [27,28,29,30,31], with small hills and extended walleyes with lots of lakes.

3. Materials and Methods

Rock samples were collected during numerous field investigations between 2018 and 2022. During this time, the discussed massifs were visited, and geological documentation of the samples was also collected. All the rock types investigated were collected in the Kolmozero and Kaustinen regions, from which only two representative samples from each area are presented in the paper. The selected rocks were targeted for thin section preparations to determine further the characteristics of the minerals discussed. Subsequently, these minerals were subjected to analyses using a Leica DM2500P polarizing optical microscope [32] and examination with a scanning electron microscope, the Hitachi SU6600, with an EDS (energy dispersive X-ray spectroscopy) attachment [33,34]. These samples were analyzed under low vacuum (10 Pa) with a 15 kV beam diameter of 0.2 µm. A total of 453 mineral analyses were performed in the microprobe (at Kaustinen 179 and Kolmozero 274, respectively). Next, the selected minerals were separated and analyzed with single-crystal X-ray diffraction. Data were collected on a Rigaku diffractometer (Rigaku, Tokyo, Japan) with CuKα radiation (λ = 1.54184 Å) at 293 K. Crystallographic refinement and data collection, as well as data reduction and analysis were performed with the CrysAlisPro v42 (Rigaku Oxford Diffraction, Tokyo, Japan) [35]. Selected single crystals were mounted on the nylon loop with oil. Structures were solved by applying direct methods using the SHELXS-86 program and refined with SHELXL−2018/3 [36,37,38] in Olex2 software [39]. Table 1 provides the experimental details for the single crystal’s X-ray measurement. These samples were also examined with the Raman technique [40,41]. Samples were measured using a Raman microscope in Via Reflex, Renishaw, UK. Optical and microscopic studies were performed in the Department of Geology, Soil Science, and Geoinformation of the Institute of Earth and Environmental Sciences, and crystal chemistry studies were performed at the Faculty of Chemistry.

4. Results

The collected pegmatite samples were analyzed using the methods described above. Below are the results of these analyses.

4.1. Rocks Geology

4.1.1. Kaustinen

Exposed near Kaustinen, the pegmatites containing LCT mineralization coexist among biotite gneisses with magnetite [42]. Macroscopically, the pegmatites are cream-gray. They are characterized by a coarse crystalline structure, a compact texture, and disorder. Macroscopic observations show large, light gray plaques of plagioclase several cm in size, accompanied by greenish microcline. Next to these minerals, gray quartz and silvery mica are visible, forming small aggregates reaching up to 1 cm in size (Figure 2B). Next to these minerals is visible spodumene, whose size reaches several centimeters and is not inferior to plagioclase. In the microscopic image, the background of the rock is made up of quartz crystals sutured between each other, characterized by wavy extinction. They are accompanied by plaques of plagioclase and particle-rich, acidic albite, which form polysynthetic twinning. Next to these minerals, microcline can be found, also having an anhedral character similar to the other minerals mentioned. Between them, muscovite is seen in large numbers, forming variously oriented aggregates of lamellae (Figure 3C,D). Alongside these minerals, there are also small clusters of clinochlore. These minerals are accompanied by spodumene, which forms hypautomorphic crystals that often approximate each other. The crystals of this mineral are sometimes woven with fine muscovite and biotite. Muscovite is accompanied by epidote. Fine grains of zircon can be seen against the mica. Next to these minerals, fine ore crystals are visible, which are opaque. These minerals, along with epidote and fine muscovite, are also present on a background of microcline.

4.1.2. Kolmozero

Among the gabbro-anorthosites that form a small intrusion in the Kolmozero belt are pegmatite bodies containing spodumene and lepidolite [43]. Macroscopically, they have a light cream-gray color. The presence of a coarse crystalline structure and a compact, disordered texture characterize them. On closer field observation, gray-cream plagioclase, gray quartz, and accompanying large crystals of greenish-cream spodumene are visible (Figure 2A). Alongside these minerals, aggregates of muscovite and lepidolite are visible. Small-sized reddish garnets and bluish apatites can be seen as accessories. Accompanying columbite–tantalite minerals form black metallic inclusions among the rock-forming minerals. Microscopic images show large crystals of quartz, which form multi-grain clusters. These crystals have an anhedral shape and are in contact with each other (Figure 3A,B). Next to them, plagioclase is visible, represented mainly by an acidic variety, rich in albite particles. Usually, polysynthetic twinning forms small clusters of anhedral crystals between quartz grains. Alongside these minerals, microcline can be seen forming small crystals accompanied by quartz and plagioclase. These minerals are interspersed with scales of muscovite, which sometimes form significant aggregates. These minerals are sometimes deformed and disentangled; among them, quartz can be found usually in the form of small grains and small crystals of epidote. Small crystals of zircon and small crystals of garnet are present in the vicinity of mica. Small ore minerals are also visible, sometimes surrounded by goethite. Fine lamellae of muscovite can also be observed against some quartz grains. Small crystals of apatite can also be seen among the leucocratic minerals. Alongside these phases, large crystals of spodumene can be seen, which usually have a hypautomorphic shape. Spodumene in these rocks is usually approximated, co-occurring with muscovite and lepidolite. In those varieties of pegmatite where the amount of lepidolite is greater, spodumene usually forms relic corroded crystals interspersed with mica.

4.2. Results of SEM-EDS Analyses

The discussed crystals of columbite and tantalite form adhesions. The micro-area in the minerals shows the co-occurrence of these phases side by side. In these minerals, in addition to niobium (columbite) and tantalum (tantalite), there are variable admixtures of iron and manganese (Figure 4 and Figure 5, Table A1). Tantalum in the minerals in question is an admixture oscillating between 11–20 wt% (see Table A1). Micro-area studies performed along the crystals in question showed that the ratio of iron to manganese and niobium to tantalum is variable throughout the crystal in both its central and edge parts. Most of these minerals have a significant admixture of niobium and a small proportion of tantalum. In the case of iron and manganese, these values are close to half (although with a predominance of manganese nitrogen). Due to the small size of the studied crystals in the samples in question and their strongly elongated shape, determining the changes in the proportions of these elements at the edge and center of these minerals is very difficult. In rocks from Kaustinen, it is accompanied by cassiterite, titanite, ilmenite, and magnetite in the form of small crystals. They coexist with galena, sphalerite, chalcopyrite, and barite. In the Kolmozero pegmatite, on the other hand, columbite–tantalite is accompanied by bixbyite, as well as clarkeite and selenite. Accompanying these minerals, quartz makes up a significant percentage of the rocks in question. Next to it is plagioclase, represented mainly by albite (84% of the crystals examined by SEM-EDS) with a small admixture of oligoclase (4%) and andesite-labradorite (6%). The pegmatites from Kaustinen also contain microcline, and the pegmatite from Kolmozero has orthoclase. In addition to these minerals, mica was found in the form of muscovite, co-mingling with spodumene and lepidolite. A small admixture of sodium (up to 5%) was found in muscovite. In addition, clinozoisite and epidote were found in pegmatites from Kaustinen. The accompanying spodumene contains a small admixture of sodium (averaging from less than 1% to 9%). Micro-area studies also made it possible to show that the coexisting phosphates are represented by a variety of hydroxyapatite, with about 3% carboxy apatite and 2% fluorapatite content.

4.3. Optical Properties of the Discussed Minerals

Macroscopically, crystals of columbite–tantalite have a black color with a metallic, rusty luster. They stand out from the minerals with which they coexist and are relatively easy to find. They have a size that reaches below 1 mm. Their quantity in Kolmozero pegmatites is much higher than that in Kaustinen, where this mineral is much rarer. In the microscopic image, Kolmozero tantalite crystals form small, jagged inclusions visible against a background of quartz and feldspar. In the case of rocks from Kolmozero, these crystals have a euhedral shape, forming much larger individuals visible against a background of spodumene and quartz. Rather, in the rocks from Kaustinen, it occurs in the form of single anhedral grains, sometimes of very elongated skeletal character. In the microscopic image, they are opaque black. In reflected light, this mineral has no clear relief and reflects light uniformly in a silvery gray color. In polarized light, the birefringence is barely visible due to the mineral’s dark coloration (Figure 6).

4.4. Spectroscopic Properties of the Discussed Minerals

Raman studies were conducted for a columbite–tantalite grain. Since it was a small grain, the spectrum shows only the most significant enhancements. The accompanying spectra show an enhancement in the region of 868 cm−1, characteristic of Nb-O vibrations. Ca-O vibrations are noted at 793 cm−1. The accompanying enhancement in the vicinity of 559 cm−1 corresponds to stretching vibrations for Nb-O. The observed vibration of 110 cm−1 corresponds to the stretching vibrations for Nb-Nb [44,45]. Some deviations from the standard spectra are due to the presence of manganese and iron admixtures in the minerals in question (Figure 7).

4.5. Single Crystals Analysis Results

The examined crystal is a mixture of columbite–tantalite with iron and manganese substitution in varying proportions. These grains are present in the discussed pegmatites from both locations (Figure 8). The defecting of the crystals due to adhesions and fissures in this case made it difficult to determine their crystal structure. A presentation of this structure is given below [46]. Figure 8 presents the unit cell packing of the investigated columbite crystal. The relatively high R1 is related to low crystal quality. The solved structures indicate that the main building elements are Nb, Fe, and oxygen. However, the Fe position can be partly occupied by Mn, but the exact ratio between Fe and Mn was impossible to determine with this technique. Other elements are possible but in amounts smaller than 0.1 per atomic position. The unit cell parameters and space group are typical for this mineral and similar to those found by Borett et al. [47]. The Qiso parameters were set to 0.03 by hand to obtain the best fit of the model to the experimental data. As expected for this type of crystal with strong bonds, all the ATP values are smaller than 0.05 (see Table A2, Table A3, Table A4 and Table A5).

5. Discussion

The discussed rocks containing columbite–tantalite mineralization are classified as granitoid pegmatites. These rocks are exposed in northern Scandinavia (in the area of the Kola Peninsula in Russia and the area of northern Finland) [48,49,50,51]. Although granitoid pegmatites in this area are visible in many places, further exploration of these rocks may increase the number of occurrences of LCT varieties. These rocks may be an interesting object of industrial exploration in the future, although their nature and the size of the observed exposures make such activities dependent on economic prosperity. An analysis of the mineralization of these pegmatites indicates that they represent the final stage of crystallization of residual melt, containing mismatched elements [52,53,54,55,56]. The presence of hydrated minerals in these rocks indicates that hydrothermal processes played a major role in the crystallization of minerals. This is also evidenced by sulfides and sulfates (barite, galena, sphalerite, and chalcopyrite). In addition, the chemical composition of ore minerals indicates the influence of fluids from the surrounding rocks [57]. This peculiarity is evident in the presence of such minerals including magnetite in the Kaustinen pegmatite and bismuth- and uranium-bearing minerals in the rocks at Kolomzero. Studies of niobium and tantalum minerals indicate that they form comagmatic adhesions that were formed during the same period of crystallization. Micro-area analyses have indicated both iron and manganese admixtures in both columbite and tantalite. In addition, there are variable amounts of niobium and tantalum in both minerals, which substitute for each other in the lattice. Additional difficulties such as cracks and close-ups prevented their separation and thus hindered the analysis of the monocrystals by the X-ray method, showing their complex nature in the rocks in question. The analysis of the Raman spectrum obtained from these minerals is similar. The rocks in question are a solid solution in which the amount of iron and manganese varies according to the tests, as also shown by the analyses carried out along the grain from its boundary to the center of the grain.

6. Conclusions

Columbite–tantalite minerals are an important source of Nb and Ta. Their presence in LCT pegmatites, together with spodumene and lepidolite, is an interesting occurrence that may be the subject of further exploration in northern Scandinavia. These pegmatites represent a granitoid variety, crystallizing among Archean and Proterozoic rocks from the last portion of magma melt involving hydrothermal processes. Detailed studies of these minerals have shown their approximations, forming a solid solution. This means that these minerals were formed in one stage of crystallization.

Author Contributions

Conceptualization, M.H. and D.K.; methodology, M.H., D.K. and U.M.; validation, M.H., D.K. and U.M.; formal analysis, M.H.; investigation, resources, M.H.; data curation, M.H. and D.K.; writing—original draft preparation, M.H.; writing—review and editing, D.K.; visualization, M.H. and D.K.; All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

The X-ray diffraction study was made possible with the support of EcoTech Complex in Lublin.

Conflicts of Interest

The authors declare no conflict of interest.

Appendix A

Table
Table A1. SEM-EDS results of the columbite–tantalite crystals and modal composition of these phases based on the proportion of measure element.
Table A1. SEM-EDS results of the columbite–tantalite crystals and modal composition of these phases based on the proportion of measure element.
PointElements Content [wt%]MineralModal Composition
OMnFeNbTa MnFeNbTaO
Kolmozero(11)/126.2015.97 29.59 Columbite0.40.62.00.06
Kolmozero(11)/228.7313.16 30.42 Columbite0.30.72.00.06
Kolmozero(11)/328.5212.60 29.13 Columbite0.30.72.00.06
Kolmozero(11)/425.4314.863.0628.41 Columbite0.30.72.00.06
Kolmozero(12)/124.0517.313.6429.53 Columbite0.40.62.00.06
Kolmozero(12)/225.2517.072.5929.50 Columbite0.40.62.00.06
Kolmozero(12)/331.42 2.8735.90 Columbite0.01.02.00.06
Kolmozero(12)/426.2211.892.1330.77 Columbite0.30.72.00.06
Kolmozero(12)/526.7111.554.8230.76 Columbite0.30.72.00.06
Kolmozero(12)/626.0611.864.6032.01 Columbite0.30.72.00.06
Kolmozero(12)/724.6713.256.3230.86 Columbite0.30.72.00.06
Kolmozero(12)/826.7412.513.0331.35 Columbite0.30.72.00.06
Kolmozero(12)/1024.7417.61 30.98 Columbite0.40.62.00.06
Kolmozero(12)/1124.4717.904.1628.17 Columbite0.40.62.00.06
Kolmozero(12)/1224.4715.224.5030.48 Columbite0.30.72.00.06
Kolmozero(26)/324.9513.71 29.16 Columbite0.30.72.00.06
Kolmozero(26)/422.1816.45 31.93 Columbite0.30.72.00.06
Kolmozero(26)/521.7115.982.3630.89 Columbite0.30.72.00.06
Kolmozero(26)/622.5813.002.8932.18 Columbite0.30.72.00.06
Kolmozero(26)/720.7317.752.3830.39 Columbite0.40.62.00.06
Kolmozero(26)/823.3212.298.6028.03 Columbite0.30.72.00.06
Kolmozero(26)/921.3515.203.6130.32 Columbite0.30.72.00.06
Kolmozero(26)/1021.5616.23 32.44 Columbite0.30.72.00.06
Kolmozero(26)/1120.2116.397.3329.11 Columbite0.40.62.00.06
Kolmozero(26)/1222.3912.444.3632.02 Columbite0.30.72.00.06
Kolmozero(26)/1321.6614.084.6430.59 Columbite0.30.72.00.06
Kolmozero(26)/1422.8615.71 31.96 Columbite0.30.72.00.06
Kolmozero(26)/1520.9715.202.2633.59 Columbite0.30.72.00.06
Kolmozero(26)/1629.96 7.98 Columbite0.01.02.00.06
Kolmozero(30)/126.9616.76 28.55 Columbite0.40.62.00.06
Kolmozero(30)/227.8717.17 27.47 Columbite0.40.62.00.06
Kolmozero(30)/329.5017.31 23.50 Columbite0.40.62.00.06
Kolmozero(30)/429.7413.110.5228.69 Columbite0.30.72.00.06
Kolmozero(30)/528.6114.992.2029.14 Columbite0.30.72.00.06
Kolmozero(30)/635.06 33.87 Columbite0.01.02.00.06
Kolmozero(30)/728.9014.543.0226.83 Columbite0.40.62.00.06
Kolmozero(30)/829.1914.361.8127.75 Columbite0.30.72.00.06
Kolmozero(30)/925.7117.474.9425.46 Columbite0.40.62.00.06
Kolmozero(31)/140.06 18.81 Columbite0.01.02.00.06
Kolmozero(34)/329.078.494.1028.98 Columbite0.20.82.00.06
Kolmozero(35)/128.2514.793.0625.94 Columbite0.40.62.00.06
Kolmozero(35)/227.9313.334.5025.95 Columbite0.30.72.00.06
Kolmozero(35)/328.0114.39 27.27 Columbite0.30.72.00.06
Kolmozero(35)/427.8815.502.5325.89 Columbite0.40.62.00.06
Kolmozero(35)/527.5416.152.0424.85 Columbite0.40.62.00.06
Kolmozero(35)/628.3611.621.7828.02 Columbite0.30.72.00.06
Kolmozero(35)/726.2416.353.2325.40 Columbite0.40.62.00.06
Kolmozero(35)/827.1912.994.0727.61 Columbite0.30.72.00.06
Kolmozero(35)/927.1614.953.4626.32 Columbite0.40.62.00.06
Kolmozero(35)/1026.4414.286.0825.26 Columbite0.40.62.00.06
Kolmozero(40)/124.5916.55 29.23 Columbite0.40.62.00.06
Kolmozero(40)/223.9011.653.7130.56 Columbite0.30.72.00.06
Kolmozero(40)/324.0414.894.2828.26 Columbite0.30.72.00.06
Kolmozero(40)/422.8915.71 29.31 Columbite0.30.72.00.06
Kolmozero(40)/525.3112.72 29.89 Columbite0.30.72.00.06
Kolmozero-2(1)/126.1417.973.4425.16 Columbite0.40.62.00.06
Kolmozero-2(4)/124.8322.65 30.17 Columbite0.40.62.00.06
Kolmozero-2(4)/326.0621.571.8228.37 Columbite0.40.62.00.06
Kaustinen-2(9)/129.8613.02 23.37 Columbite0.40.62.00.06
Kaustinen-2(9)/232.239.854.5914.86 Columbite0.40.62.00.06
Kaustinen-2(10)/134.57 3.1821.38 Columbite0.01.02.00.06
Kaustinen-2(10)/227.4912.739.7617.55 Columbite0.40.62.00.06
Kaustinen-2(10)/1033.175.451.8410.43 Columbite0.30.72.00.06
Kolmozero(12)/924.4712.143.2330.076.80Tantalite0.30.71.60.46
Kolmozero(30)/1024.9714.961.6225.3811.89Tantalite0.40.61.40.66
Kaustinen-2(10)/327.749.594.1510.4218.41Tantalite0.50.50.71.36
Kaustinen-2(10)/425.569.716.5215.3620.94Tantalite0.40.60.81.26
Kaustinen-2(10)/527.767.205.7416.1517.87Tantalite0.30.70.91.16
Kaustinen-2(10)/626.6110.027.0517.3415.39Tantalite0.40.61.10.96
Kaustinen-2(10)/725.3411.963.2419.0416.27Tantalite0.40.61.10.96
Kaustinen-2(10)/825.6111.143.9220.8713.92Tantalite0.30.71.20.86
Kaustinen-2(10)/927.7912.335.3415.6611.90Tantalite0.40.61.10.96
Kolmozero-2(4)/124.8322.65 30.17 Columbite0.40.62.00.06
Kolmozero-2(4)/220.5421.86 31.7212.52Tantalite0.40.61.40.66
Kolmozero-2(4)/326.0621.571.8228.37 Columbite0.40.62.00.06
Kolmozero-2(4)/419.0220.869.7225.3914.92Tantalite0.50.51.30.76

Appendix B

Table
Table A2. Crystal data and structure refinement for Columbite_autored.
Table A2. Crystal data and structure refinement for Columbite_autored.
Identification CodeColumbite_Autored
Empirical formulaFeNb2O6
Formula weight337.67
Temperature/K294
Crystal systemOrthorhombic
Space groupPbcn
a/Å14.281(2)
b/Å5.7366(7)
c/Å5.1234(5)
α/°90
β/°90
γ/°90
Volume/Å3419.73(9)
Z4
ρcalc g/cm35.344
μ/mm−170.926
F(000)624.0
Crystal size/mm30.4 × 0.4 × 0.2
RadiationCu Kα (λ = 1.54184)
2θ range for data collection/°12.396 to 135.856
Index ranges−15 ≤ h ≤ 16, −6 ≤ k ≤ 6, −5 ≤ l ≤ 6
Reflections collected1425
Independent reflections361 [Rint = 0.0351, Rsigma = 0.0211]
Data/restraints/parameters361/0/17
Goodness-of-fit on F22.703
Final R indexes [I > =2σ (I)]R1 = 0.1743, wR2 = 0.5169
Final R indexes [all data]R1 = 0.1859, wR2 = 0.5396
Largest diff. peak/hole/e Å−341.40/−7.29
Table
Table A3. Fractional atomic coordinates (×104) and equivalent isotropic displacement parameters (Å2 × 103) for Columbite_autored. Ueq is defined as 1/3 of the trace of the orthogonalized UIJ tensor.
Table A3. Fractional atomic coordinates (×104) and equivalent isotropic displacement parameters (Å2 × 103) for Columbite_autored. Ueq is defined as 1/3 of the trace of the orthogonalized UIJ tensor.
AtomxyzU(eq)
Nb16641.6(14)8256(6)7555(3)−1(2)
Fe150006716(12)2500−1(4)
O17568(14)6200(30)5910(40)30
O35778(14)3830(30)4020(40)30
O25961(15)8960(30)4280(40)30
Table
Table A4. Bond lengths for Columbite_autored.
Table A4. Bond lengths for Columbite_autored.
AtomAtomLength/ÅAtomAtomLength/Å
Nb1Nb1 13.250(4)Fe1O32.14(2)
Nb1Nb1 23.250(4)Fe1O3 82.14(2)
Nb1O1 32.20(2)Fe1O22.09(2)
Nb1O1 42.08(2)Fe1O2 82.09(2)
Nb1O11.96(2)O1Nb1 92.08(2)
Nb1O3 51.88(2)O1Nb1 102.20(2)
Nb1O2 22.07(2)O3Nb1 71.88(2)
Nb1O21.98(2)O3Fe1 62.13(2)
Fe1O3 62.13(2)O2Nb1 12.07(2)
Fe1O3 72.13(2)
1 +X, 2 − Y, −1/2 + Z; 2 +X, 2 − Y, 1/2 + Z; 3 3/2 − X, 1/2 + Y, +Z; 4 3/2 − X, 3/2 − Y, 1/2 + Z; 5 +X, 1 − Y, ½ + Z; 6 1 − X, 1 − Y, 1 − Z; 7 +X, 1 − Y, −1/2 + Z; 8 1 − X, +Y, 1/2 − Z; 9 3/2 − X, 3/2 − Y, −1/2 + Z; 10 3/2 − X, −1/2 + Y, +Z.
Table
Table A5. Bond angles for Columbite_autored.
Table A5. Bond angles for Columbite_autored.
AtomAtomAtomAngle/°AtomAtomAtomAngle/°
Nb1 1Nb1Nb1 2104.03(18)O2Nb1O1 476.8(9)
O1 3Nb1Nb1 242.0(5)O2Nb1O2 288.5(7)
O1Nb1Nb1 191.8(6)O3Fe1O3 678.7(11)
O1Nb1Nb1 2135.1(6)O3 7Fe1O3 8162.9(11)
O1 4Nb1Nb1 280.2(6)O3 8Fe1O3 685.3(7)
O1 4Nb1Nb1 139.2(6)O3 7Fe1O385.3(7)
O1 3Nb1Nb1 1124.0(6)O3 7Fe1O3 681.5(8)
O1Nb1O1 487.2(5)O3 8Fe1O381.5(8)
O1Nb1O1 394.6(5)O2 6Fe1O3167.3(9)
O1 3Nb1O1 485.6(7)O2Fe1O3 796.6(7)
O1Nb1O295.1(8)O2Fe1O3 893.9(7)
O1Nb1O2 2164.7(10)O2Fe1O3 6167.3(9)
O3 5Nb1Nb1 294.5(6)O2 6Fe1O3 688.6(7)
O3 5Nb1Nb1 1135.1(7)O2 6Fe1O3 896.6(7)
O3 5Nb1O1103.3(9)O2Fe1O388.6(7)
O3 5Nb1O1 397.1(8)O2 6Fe1O3 793.9(7)
O3 5Nb1O1 4168.9(9)O2 6Fe1O2104.0(11)
O3 5Nb1O2 290.8(8)Nb1O1Nb1 9130.0(11)
O3 5Nb1O298.4(8)Nb1 10O1Nb1 998.8(8)
O2 2Nb1Nb1 235.7(6)Nb1O1Nb1 10129.1(10)
O2Nb1Nb1 2122.8(6)Nb1 7O3Fe1 8125.7(10)
O2 2Nb1Nb1 182.1(6)Nb1 7O3Fe1133.7(11)
O2Nb1Nb1 137.5(6)Fe1 8O3Fe198.5(8)
O2 2Nb1O1 377.6(8)Nb1O2Nb1 1106.8(10)
O2Nb1O1 3159.4(8)Nb1O2Fe1124.5(10)
O2 2Nb1O1 479.2(9)Nb1 1O2Fe1126.7(10)
1 +X, 2 − Y, −1/2 + Z; 2 +X, 2 − Y, 1/2 + Z; 3 3/2 − X, 1/2 + Y, +Z; 4 3/2 − X, 3/2 − Y, 1/2 + Z; 5 +X, 1 − Y, ½ + Z; 6 1 − X, 1 − Y, 1 − Z; 7 +X, 1 − Y, −1/2 + Z; 8 1 − X, +Y, 1/2 − Z; 9 3/2 − X, 3/2 − Y, −1/2 + Z; 10 3/2 − X, −1/2 + Y, +Z.

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Crystals 13 00612 g001 550
Figure 1. Simplified geological—tectonic map of the N Skandinavia (after [17]) with the samples’ location.
Figure 1. Simplified geological—tectonic map of the N Skandinavia (after [17]) with the samples’ location.
Crystals 13 00612 g001
Crystals 13 00612 g002 550
Figure 2. Macro photographs of the typical examples of LCT pegmatites from Kolmozero (A) and Kaustinen (B). Abbreviations: qtz—quartz, mu—muscovite, pl—plagioclase, sp—spodumene.
Figure 2. Macro photographs of the typical examples of LCT pegmatites from Kolmozero (A) and Kaustinen (B). Abbreviations: qtz—quartz, mu—muscovite, pl—plagioclase, sp—spodumene.
Crystals 13 00612 g002
Crystals 13 00612 g003 550
Figure 3. Microphotographs of the rocks from Kolmozero (A,B) and Kaustinen (C,D) with the typical association of the minerals and structures of rocks. There are present and microcline (mi), plagioclase (pl), quartz (qtz), muscovite (mu) and spodumene (sp).
Figure 3. Microphotographs of the rocks from Kolmozero (A,B) and Kaustinen (C,D) with the typical association of the minerals and structures of rocks. There are present and microcline (mi), plagioclase (pl), quartz (qtz), muscovite (mu) and spodumene (sp).
Crystals 13 00612 g003
Crystals 13 00612 g004 550
Figure 4. Backscattering electron microphotography of the columbite–tantalite grains with the marked analysis points.
Figure 4. Backscattering electron microphotography of the columbite–tantalite grains with the marked analysis points.
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Crystals 13 00612 g005 550
Figure 5. Proportion of the Fe, Mn, Nb, and Ta ions of the measured crystals.
Figure 5. Proportion of the Fe, Mn, Nb, and Ta ions of the measured crystals.
Crystals 13 00612 g005
Crystals 13 00612 g006 550
Figure 6. Images of columbite–tantalite (col-tan) in transmitted light (A,D) and reflected light (B,C,E,F), and under unpolarized light (B,E) and polarized light (A,C,D,F), showing the optical properties of this sample.
Figure 6. Images of columbite–tantalite (col-tan) in transmitted light (A,D) and reflected light (B,C,E,F), and under unpolarized light (B,E) and polarized light (A,C,D,F), showing the optical properties of this sample.
Crystals 13 00612 g006
Crystals 13 00612 g007 550
Figure 7. Raman spectrum for the columbite–tantalite crystals from Kolmozero.
Figure 7. Raman spectrum for the columbite–tantalite crystals from Kolmozero.
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Crystals 13 00612 g008 550
Figure 8. Crystal structure of columbite–tantalite (red line represents the x-axis and blue the z-axis).
Figure 8. Crystal structure of columbite–tantalite (red line represents the x-axis and blue the z-axis).
Crystals 13 00612 g008
Table
Table 1. Single crystals X-ray diffraction results for all measured minerals.
Table 1. Single crystals X-ray diffraction results for all measured minerals.
MineralColumbite
Empirical formulaFeNb2O6
Temperature/K294
Crystal systemOrthorhombic
Space groupPbcn
a/Å14.281(2)
b/Å5.7366(7)
c/Å5.1234(5)
α/°90
β/°90
γ/°90
Volume/Å3419.73(9)
Z4
ρcalc g/cm35.344
Crystal size/mm30.4 × 0.4 × 0.2
Data/restraints/parameters361/0/17
Goodness-of-fit on F22.703
Final R indexes [I > =2σ (I)]R1 = 0.1743,
wR2 = 0.5169
Largest diff. peak/hole/e Å−341.40/−7.29
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Huber, M.; Kamiński, D.; Maciołek, U. Columbite–Tantalite from Northern Scandinavia (Kaustinen, Kolmozero) Pegmatites: An Optical and Spectroscopic Properties. Crystals 2023, 13, 612. https://doi.org/10.3390/cryst13040612

AMA Style

Huber M, Kamiński D, Maciołek U. Columbite–Tantalite from Northern Scandinavia (Kaustinen, Kolmozero) Pegmatites: An Optical and Spectroscopic Properties. Crystals. 2023; 13(4):612. https://doi.org/10.3390/cryst13040612

Chicago/Turabian Style

Huber, Miłosz, Daniel Kamiński, and Urszula Maciołek. 2023. "Columbite–Tantalite from Northern Scandinavia (Kaustinen, Kolmozero) Pegmatites: An Optical and Spectroscopic Properties" Crystals 13, no. 4: 612. https://doi.org/10.3390/cryst13040612

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