Dellaventuraite is a new amphibole species from the Kajlidongri manganese mine, Jhabua District, Madhya Pradesh, India. It occurs with leakeite, kornite, albite, braunite, and bixbyite associated with cross-cutting epigenetic veins that have reacted with regionally metamorphosed rocks containing Mn-rich minerals (braunite, bixbyite, jacobsite, spessartine) to produce Mn-rich amphiboles, Mn-rich pyroxenes, Mn-rich mica, piemontite, and manganophyllite. Dellaventuraite occurs as anhedral grains, the color of which varies from pink to red, depending on Mn content. It is brittle, H = 5, D-calc = 3.184 g/cm(3), has a pale pink streak, vitreous luster, and does not fluoresce in ultraviolet light; it has perfect cleavage on {110} and conchoidal fracture. In transmitted plane-polarized light, dellaventuraite is strongly pleochroic X = pale mauve-brown, Y similar to Z = dark red-brown; Y <^> a = 20degrees (in beta obtuse), Z = b, with absorption X < Y similar to Z. It is biaxial positive, eta(alpha) = 1.688 +/- 0.0003, eta(beta) = 1.692 +/- 0.005, eta(gamma) = 1.721 +/- 0.003, 2V((obs)) = 49 +/- 3degrees, 2V((calc)) = 41degrees. Dellaventuraite is monoclinic, space group C2/m, a = 9.808(1), b = 17.840(2), c = 5.2848(5) Angstrom, gamma = 104.653(1)degrees, V = 894.6(2) Angstrom(3), Z = 2. The strongest ten X-ray diffraction lines in the powder pattern are [d(l,hkl)]: 2.697(10,151), 2.542(9,-202), 3.127(8,310), 3.378(7,131),2.154(7,261),1.434 (7,-661),4.450(6,021), 8.459(5,110), 2.727(5,-331),2.328(5,-351). Analysis by a combination of electron microprobe, SIMS and crystal-structure refinement gives SiO2 = 54.22, Al2O3 = 0.81, TiO2 = 5.45, Fe2O3 = 6.44, Mn2O3 = 7.57, ZnO = 0.12, NiO = 0.16, MgO = 8.26, Li2O = 1.53, CaO = 1.85, Na2O = 8.12, K2O = 2.12, H2O = 0.80, Cr, V, F, Cl not detected, sum 97.41 wt%. The formula unit, calculated on the basis of 24(O,OH,F) is (K0.40Na0.61)(Na1.71Ca0.29) (Mg1.81Zn0.01Ni0.002Li0.90Fe0.713+Mn0.853+Ti0.604+Al0.10)(Si7.96Al0.04)O-22[(OH0.80 O-1.20]; the ideal end-member compostion NaNa2(MgMn23+LiTi4+)Si8O22O2. The crystal structure of dellaventuraite was refined to an R index of 3.8% using MoKalpha. X-ray intensity data. The M1 site is occupied by Ti4+, Mn3+, and Mg in approximately equal amounts, the M2 site is occupied primarily by Mg and Fe3+, and M3 is occupied by Li with minor Mg and Mn2+. Local bond-valence considerations suggest that O2- at O3 is linked to Ti4+Mg or Mn3+Mn3+ at the adjacent M I sites, and that OH at O3 is linked to MgMg at the adjacent M1 sites.
Dellaventuraite, NaNa2(MgMn32+Ti 4+Li)Si8O22O2, a new anhydrous amphibole from the Kajlidongri manganese mine, Jhabua district, Madhya Pradesh, India.
Ottolini L;
2005
Abstract
Dellaventuraite is a new amphibole species from the Kajlidongri manganese mine, Jhabua District, Madhya Pradesh, India. It occurs with leakeite, kornite, albite, braunite, and bixbyite associated with cross-cutting epigenetic veins that have reacted with regionally metamorphosed rocks containing Mn-rich minerals (braunite, bixbyite, jacobsite, spessartine) to produce Mn-rich amphiboles, Mn-rich pyroxenes, Mn-rich mica, piemontite, and manganophyllite. Dellaventuraite occurs as anhedral grains, the color of which varies from pink to red, depending on Mn content. It is brittle, H = 5, D-calc = 3.184 g/cm(3), has a pale pink streak, vitreous luster, and does not fluoresce in ultraviolet light; it has perfect cleavage on {110} and conchoidal fracture. In transmitted plane-polarized light, dellaventuraite is strongly pleochroic X = pale mauve-brown, Y similar to Z = dark red-brown; Y <^> a = 20degrees (in beta obtuse), Z = b, with absorption X < Y similar to Z. It is biaxial positive, eta(alpha) = 1.688 +/- 0.0003, eta(beta) = 1.692 +/- 0.005, eta(gamma) = 1.721 +/- 0.003, 2V((obs)) = 49 +/- 3degrees, 2V((calc)) = 41degrees. Dellaventuraite is monoclinic, space group C2/m, a = 9.808(1), b = 17.840(2), c = 5.2848(5) Angstrom, gamma = 104.653(1)degrees, V = 894.6(2) Angstrom(3), Z = 2. The strongest ten X-ray diffraction lines in the powder pattern are [d(l,hkl)]: 2.697(10,151), 2.542(9,-202), 3.127(8,310), 3.378(7,131),2.154(7,261),1.434 (7,-661),4.450(6,021), 8.459(5,110), 2.727(5,-331),2.328(5,-351). Analysis by a combination of electron microprobe, SIMS and crystal-structure refinement gives SiO2 = 54.22, Al2O3 = 0.81, TiO2 = 5.45, Fe2O3 = 6.44, Mn2O3 = 7.57, ZnO = 0.12, NiO = 0.16, MgO = 8.26, Li2O = 1.53, CaO = 1.85, Na2O = 8.12, K2O = 2.12, H2O = 0.80, Cr, V, F, Cl not detected, sum 97.41 wt%. The formula unit, calculated on the basis of 24(O,OH,F) is (K0.40Na0.61)(Na1.71Ca0.29) (Mg1.81Zn0.01Ni0.002Li0.90Fe0.713+Mn0.853+Ti0.604+Al0.10)(Si7.96Al0.04)O-22[(OH0.80 O-1.20]; the ideal end-member compostion NaNa2(MgMn23+LiTi4+)Si8O22O2. The crystal structure of dellaventuraite was refined to an R index of 3.8% using MoKalpha. X-ray intensity data. The M1 site is occupied by Ti4+, Mn3+, and Mg in approximately equal amounts, the M2 site is occupied primarily by Mg and Fe3+, and M3 is occupied by Li with minor Mg and Mn2+. Local bond-valence considerations suggest that O2- at O3 is linked to Ti4+Mg or Mn3+Mn3+ at the adjacent M I sites, and that OH at O3 is linked to MgMg at the adjacent M1 sites.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
