Referenza:
▪ Sokolova, E., Day, M.C., Hawthorne, F.C., Kristiansen, R. (2018): Heyerdahlite, Na3Mn7Ti2(Si4O12)2O2(OH)4F(H2O)2, a new mineral of the astrophyllite supergroup from the Larvik Plutonic complex, Norway: Description and crystal structure. Mineralogical Magazine, 82, 243-255.
Abstract:
Heyerdahlite, ideally Na3Mn7Ti2(Si4O12)2O2(OH)4F(H2O)2, is a new astrophyllite-supergroup mineral from the Larvik Plutonic complex, Norway. Heyerdahlite was found in a nepheline-syenite pegmatite with albite, aegirine, hastingsite/magnesio-hastingsite, kupletskite, lorenzenite and pyrophanite. Heyerdahlite is colourless to pale brown, transparent and has a vitreous luster. Mohs hardness is 3, Dcalc. = 3.245 g/cm3. Heyerdahlite is biaxial (+), α = 1.694(2), β = 1.710(5), γ = 1.730(5), 2Vmeas. = 80(4)°; 2Vcalc. = 84.5°. Cleavage is perfect parallel to {001}. The empirical formula based on 32.18 (O+F) apfu is (Na1.18K0.68Rb0.12Cs0.01Pb0.01)S2Na1.00 (Mn6.29Zn0.23Mg0.07Zr0.04Fe2+0.03Ca0.01Na0.34)S7.01(Ti1.78Nb0.17Mg0.03Zr0.02)S2(Si8.03O24)O2 [(OH)3.92F0.08]S4F1.00[(H2O)1.18o0.82]S2, Z = 1. Heyerdahlite is triclinic, space group P-1, a 5.392(2), b 11.968(4), c 11.868(4) Å, α 112.743(8), β 94.816(7), γ 103.037(8)°, V 675.6(7) Å3. The crystal structure was refined to R1 = 4.44% for 3577 unique (Fo > 4σF) reflections. In the crystal structure of heyerdahlite, there are four [4]T sites occupied by Si. The [6]D site is occupied mainly by Ti. The T4O12 astrophyllite ribbons composed of SiO4 tetrahedra and D octahedra constitute the H (Heteropolyhedral) sheet. In the O (Octahedral) sheet, there are four Mn-dominant [6]M(1–4) sites. Two H sheets and one central O sheet form the HOH block, and adjacent HOH blocks link via a common XPD anion of the two D octahedra. In the I (Intermediate) block between HOH blocks, there are two interstitial cation sites, A and B, and a WA site, partly occupied by H2O. The A site splits into two sites, [12]A(1) and [6]A(2), partly occupied by K and Na, respectively, with A(1)–A(2) = 0.754 Å. The aggregate content of the A site is ideally Na2 apfu. The [10]B site is occupied by Na. The WA site is ideally occupied by (H2O)2 pfu. The mineral is named heyerdahlite after the Norwegian explorer Thor Heyerdahl (1914-2002), who was born in Larvik.
▪ Sokolova, E., Day, M.C., Hawthorne, F.C., Kristiansen, R. (2018): Heyerdahlite, Na3Mn7Ti2(Si4O12)2O2(OH)4F(H2O)2, a new mineral of the astrophyllite supergroup from the Larvik Plutonic complex, Norway: Description and crystal structure. Mineralogical Magazine, 82, 243-255.
Abstract:
Heyerdahlite, ideally Na3Mn7Ti2(Si4O12)2O2(OH)4F(H2O)2, is a new astrophyllite-supergroup mineral from the Larvik Plutonic complex, Norway. Heyerdahlite was found in a nepheline-syenite pegmatite with albite, aegirine, hastingsite/magnesio-hastingsite, kupletskite, lorenzenite and pyrophanite. Heyerdahlite is colourless to pale brown, transparent and has a vitreous luster. Mohs hardness is 3, Dcalc. = 3.245 g/cm3. Heyerdahlite is biaxial (+), α = 1.694(2), β = 1.710(5), γ = 1.730(5), 2Vmeas. = 80(4)°; 2Vcalc. = 84.5°. Cleavage is perfect parallel to {001}. The empirical formula based on 32.18 (O+F) apfu is (Na1.18K0.68Rb0.12Cs0.01Pb0.01)S2Na1.00 (Mn6.29Zn0.23Mg0.07Zr0.04Fe2+0.03Ca0.01Na0.34)S7.01(Ti1.78Nb0.17Mg0.03Zr0.02)S2(Si8.03O24)O2 [(OH)3.92F0.08]S4F1.00[(H2O)1.18o0.82]S2, Z = 1. Heyerdahlite is triclinic, space group P-1, a 5.392(2), b 11.968(4), c 11.868(4) Å, α 112.743(8), β 94.816(7), γ 103.037(8)°, V 675.6(7) Å3. The crystal structure was refined to R1 = 4.44% for 3577 unique (Fo > 4σF) reflections. In the crystal structure of heyerdahlite, there are four [4]T sites occupied by Si. The [6]D site is occupied mainly by Ti. The T4O12 astrophyllite ribbons composed of SiO4 tetrahedra and D octahedra constitute the H (Heteropolyhedral) sheet. In the O (Octahedral) sheet, there are four Mn-dominant [6]M(1–4) sites. Two H sheets and one central O sheet form the HOH block, and adjacent HOH blocks link via a common XPD anion of the two D octahedra. In the I (Intermediate) block between HOH blocks, there are two interstitial cation sites, A and B, and a WA site, partly occupied by H2O. The A site splits into two sites, [12]A(1) and [6]A(2), partly occupied by K and Na, respectively, with A(1)–A(2) = 0.754 Å. The aggregate content of the A site is ideally Na2 apfu. The [10]B site is occupied by Na. The WA site is ideally occupied by (H2O)2 pfu. The mineral is named heyerdahlite after the Norwegian explorer Thor Heyerdahl (1914-2002), who was born in Larvik.