TY - JOUR
T1 - Jakobssonite, CaAlF5, a new mineral from fumaroles at the Eldfell and Hekla volcanoes, Iceland
AU - Balic Zunic, Tonci
AU - Garavelli, A.
AU - Mitolo, D.
AU - Acquafredda, P.
AU - Leonardsen, E.
PY - 2012
Y1 - 2012
N2 - The new mineral jakobssonite, ideally CaAlF5, was first found in crusts collected in 1988 from a fumarole on the Eldfell volcano, Heimaey Island, Iceland. It was subsequently found in similar crusts collected in 1991 from a fumarole on the Hekla volcano, Iceland. It is associated with leonardsenite (IMA2011-059), ralstonite, heklaite, anhydrite, gypsum, jarosite, hematite, opal and several fluoride minerals that have not been fully characterized. Jakobssonite occurs as soft white fragile crusts of acicular crystals <50 μm long. Its calculated density is 2.89 g cm-3. Chemical analyses by energy-dispersive spectrometry on a scanning electron microscope produced a mean elemental composition as follows: Ca, 18.99; Al, 18.55; Mg, 1.33; Na, 0.33; F, 50.20; O, 10.39; total 99.79 wt.%. The empirical chemical formula, calculated on the basis of 7 atoms per formula unit with all of the oxygen as OH, is (Ca0.73Mg0.09Na 0.02)S 0.84Al1.06F4.09(OH) 1.01. Jakobssonite is monoclinic, space group C2/c, with a = 8.601(1), b = 6.2903(6), c = 7.2190(7) Å, β = 114.61(1)o, V = 355.09(8) Å3and Z = 4. The crystal structure contains chains of [AlF6] octahedra which run parallel to the c axis. These chains are interconnected by chains of [CaF7] pentagonal bipyramids. Jakobssonite is isostructural with several other CaM III F 5 compounds. The eight strongest lines in the powder diffraction diagram [d in Å (I) (hkl)] are as follows: 4.91 (18) (110), 3.92 (76) (200), 3.15 (68) (020), 3.13 (100) (112), 2.27 (22) (222), 1.957 (21) (400), 1.814 (20) (132), 1.805 (22) (204). The chemical and crystal-structure analyses of jakobssonite are similar to synthetic CaAlF5 with minor substitutions of light elements (e.g. Na) or vacancies for Ca, and OH for F.
AB - The new mineral jakobssonite, ideally CaAlF5, was first found in crusts collected in 1988 from a fumarole on the Eldfell volcano, Heimaey Island, Iceland. It was subsequently found in similar crusts collected in 1991 from a fumarole on the Hekla volcano, Iceland. It is associated with leonardsenite (IMA2011-059), ralstonite, heklaite, anhydrite, gypsum, jarosite, hematite, opal and several fluoride minerals that have not been fully characterized. Jakobssonite occurs as soft white fragile crusts of acicular crystals <50 μm long. Its calculated density is 2.89 g cm-3. Chemical analyses by energy-dispersive spectrometry on a scanning electron microscope produced a mean elemental composition as follows: Ca, 18.99; Al, 18.55; Mg, 1.33; Na, 0.33; F, 50.20; O, 10.39; total 99.79 wt.%. The empirical chemical formula, calculated on the basis of 7 atoms per formula unit with all of the oxygen as OH, is (Ca0.73Mg0.09Na 0.02)S 0.84Al1.06F4.09(OH) 1.01. Jakobssonite is monoclinic, space group C2/c, with a = 8.601(1), b = 6.2903(6), c = 7.2190(7) Å, β = 114.61(1)o, V = 355.09(8) Å3and Z = 4. The crystal structure contains chains of [AlF6] octahedra which run parallel to the c axis. These chains are interconnected by chains of [CaF7] pentagonal bipyramids. Jakobssonite is isostructural with several other CaM III F 5 compounds. The eight strongest lines in the powder diffraction diagram [d in Å (I) (hkl)] are as follows: 4.91 (18) (110), 3.92 (76) (200), 3.15 (68) (020), 3.13 (100) (112), 2.27 (22) (222), 1.957 (21) (400), 1.814 (20) (132), 1.805 (22) (204). The chemical and crystal-structure analyses of jakobssonite are similar to synthetic CaAlF5 with minor substitutions of light elements (e.g. Na) or vacancies for Ca, and OH for F.
U2 - 10.1180/minmag.2012.076.3.22
DO - 10.1180/minmag.2012.076.3.22
M3 - Journal article
SN - 0026-461X
VL - 76
SP - 751
EP - 760
JO - Mineralogical Magazine
JF - Mineralogical Magazine
IS - 3
ER -