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- Holtstam, Dan, 1963-, et al.
(författare)
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An 18th century find of an erratic lazulite-andalusite-quartz boulder in Södermanland, Sweden, and its implications
- 2019
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Ingår i: GFF. - Stockholm : Taylor & Francis. - 1103-5897 .- 2000-0863. ; 141:3, s. 216-221
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Tidskriftsartikel (refereegranskat)abstract
- At some point in the 1750s, a jeweller-apprentice by the name Jacob Hässelgren found an erratic bouldernext to the Eskilstuna country road in the neighbourhood of Ärla in Södermanland. It contained a deep bluemass of lazulite, at the time an unknown mineral. Pieces of the find eventually reached Daniel Tilas, TorbernBergman and Axel Fredrik Cronstedt ˗ renowned natural scientists in Sweden ˗ but no detailed studies of thematerial seem to have been carried out by them. Two fragments of the original boulder are still preserved,and a recent examination shows them to consist of mainly lazulite, andalusite, quartz, pyrophyllite, augeliteand svanbergite. The average composition of lazulite is Mg0.700Fe2+0.261Mn0.003Al1.954Fe3+0.017 P2.031O8(OH)2.The mineral assemblage is characteristic of known occurrences of phosphate-Al silicate-quartz appearingalong the Protogine Zone in southern Sweden. Transportation of the boulder from its source rock, likely tobe located somewhere along the Protogine Zone, ought to have occurred in connection with the developmentof the Fennoscandian ice sheet during the final Weichselian deglaciation, and the material waspossibly discharged from floating ice on the Yoldia Sea.
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- Holtstam, Dan, 1963-
(författare)
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Den outsläckliga törsten efter kobolt
- 2019
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Ingår i: Geologiskt forum. - Stockholm. - 1104-4721. ; 2019:103, s. 25-28
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- The shift to electric vehicles and the growing production of rechargeable batteries needed in these have dramatically increased the global demand for cobalt. Most of the metal comes from less stable areas in the world, which makes the supply precarious. The article describes the present situation (in Swedish), and gives a brief overview of the main sources of cobalt in the world today and the prospects for exploiting reserves in Sweden.
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- Holtstam, Dan, 1963-, et al.
(författare)
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Hjalmarite, a new Na-Mn member of the amphibole supergroup, from Mn skarn in the Långban deposit, Värmland, Sweden.
- 2019
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Ingår i: European journal of mineralogy. - : Schweizerbart. - 0935-1221 .- 1617-4011. ; 31, s. 565-574
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Tidskriftsartikel (refereegranskat)abstract
- Hjalmarite, ideally ANaB(NaMn)CMg5TSi8O22W(OH)2, is a new root-name member of the amphibole supergroup, discovered in skarn from the Långban Fe-Mn-(Ba-As-Pb-Sb-Be-B) deposit, Filipstad, Värmland, Sweden (IMA-CNMNC 2017-070). It occurs closely associated with mainly rhodonite and quartz. It is grayish white with vitreous luster and non-fluorescent. The crystals are up to 5 mm in length and display splintery fracture and perfect cleavage along {110}. Hjalmarite is colorless (non-pleochroic) in thin section and optically biaxial (-), with α = 1.620(5), β = 1.630(5), γ = 1.640(5). The calculated density is 3.12 Mg/m3. Average VHN100 is 782, corresponding to circa 5½ Mohs. An empirical formula, derived from EPMA analyses in combination with crystal structure refinements, is (Na0.84K0.16)Σ1(Na1.01Mn0.55Ca0.43Sr0.01) Σ2(Mg3.83Mn1.16Al0.01) Σ5(Si7.99Al0.01) Σ8O22(OH1.92F0.08)Σ2. An infra-red spectrum of hjalmarite shows distinct absorption bands at 3673 cm-1 and 3731 cm-1 polarized in the α direction. The eight strongest Bragg peaks in the powder X-ray diffraction pattern are [d (Å), I (%), (hkl)]: 3.164, 100, (310); 2.837, 50, (330); 8.50, 44, (110); 3.302; 40, (240); 1.670, 34, (461); 1.448, 32, (-661); 2.727, 30, (151); 2.183, 18 (261).Single-crystal X-ray diffraction data were collected at 298 K and 180 K. The crystal structure was refined in space group C2/m to R1=2.6% [I>2(I)], with observed unit-cell parameters a = 9.9113(3), b = 18.1361(4), c = 5.2831(5) Å, β=103.658(5)° and V = 922.80(9) Å3 at ambient temperature. The A and M(4) sites split into A(m) (K+), A(2) (Na+), and M(4’) (Mn2+) subsites, respectively. Among the octahedrally coordinated C group cations, Mn2+ orders strongly at the M(2) site. No significant violation of C2/m symmetry or change in the structure topology is detected at low temperature (R1=2.1%). The hjalmarite-bearing skarn formed at peak regional metamorphism, T ≥ 600°C, at conditions of high SiO2 activity and relatively low oxygen fugacity. The mineral name honors the Swedish geologist and mineralogist S.A. Hjalmar Sjögren (1856–1922).
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| 5. |
- Holtstam, Dan, 1963-, et al.
(författare)
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Recognition and approval of potassic-richerite, an amphibole supergroup mineral, from the Pajsberg mines, Filipstad, Sweden.
- 2019
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Ingår i: Mineralogy and Petrology. - : Springer. - 0930-0708 .- 1438-1168. ; 113, s. 7-16
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Tidskriftsartikel (refereegranskat)abstract
- Potassic-richterite, ideally AKB(NaCa)CMg5TSi8O22W(OH)2, is recognized as a valid member of the amphibole supergroup (IMA CNMNC 2017–102). Type material is from the Pajsberg Mn-Fe ore field, Filipstad, Värmland, Sweden, where the mineral occurs in a Mn-rich skarn, closely associated with mainly phlogopite, jacobsite and tephroite. The megascopic colour is straw yellow to grayish brown and the luster vitreous. The nearly anhedral crystals, up to 4 mm in length, are pale yellow (non-pleochroic) in thin section andoptically biaxial (−), with α = 1.615(5), β = 1.625(5), γ = 1.635(5). The calculated density is 3.07 g·cm−1. VHN100 is in the range 610–946. Cleavage is perfect along {110}. EPMA analysis in combination with Mössbauer and infrared spectroscopy yields the empirical formula (K0.61Na0.30Pb0.02)Σ0.93(Na1.14Ca0.79Mn0.07)Σ2(Mg4.31Mn0.47Fe3+0.20)Σ5(Si7.95Al0.04Fe3+0.01)Σ8O22(OH1.82F0.18)Σ2 for a fragmentused for collection of single-crystal X-ray diffraction data. The infra-red spectra show absorption bands at 3672 cm−1 and 3736 cm−1 for the α direction. The crystal structure was refined in space group C2/m to R1=3.6% [I >2σ(I)], with resulting cellparameters a = 9.9977(3) Å, b = 18.0409(4) Å, c = 5.2794(2) Å, γ = 104.465(4)°, V = 922.05(5) Å3 and Z=2. The A and M(4) sites split into A(m) (K+), A(2/m) (Na+), A(2) (Pb2+), and M(4′) (Mn2+) subsites, respectively. The remaining Mn2+ is strongly ordered at theoctahedrally coordinated M(2) site, possibly together with most of Fe3+. The skarn bearing potassic-richterite formed at peak metamorphism, under conditions of low SiO2 and Al2O3 activities and relatively high oxygen fugacities.
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