Reference:
▪ Kampf, A.R., Nash, B.P., Marty, J., Hughes, J.M. (2017): Mesaite, CaMn2+5(V2O7)3·12H2O, a new vanadate mineral from the Packrat mine, near Gateway, Mesa County, Colorado, USA. Mineralogical Magazine, 81, 319–327.
Abstract:
Mesaite (IMA2015-069), ideally CaMn2+5(V2O7)3·12H2O, is a new mineral from the Packrat mine, Gateway district, Mesa County, Colorado. Crystals of mesaite occur as orangish red blades up to 0.1 mm long. The streak is light pinkish orange and the lustre is vitreous, transparent. Mesaite has a brittle tenacity, {010} perfect cleavage; fracture is irregular, and no parting was observed. The mineral has a Mohs hardness ca 2. The measured density of mesaite is 2.74(1) g cm-3. Mesaite is biaxial (-), α = 1.760(calc), β = 1.780(5), γ = 1.795(5) in white light; the measured 2V value = 81(2)°. Dispersion is strong, r < v, and pleochroism is present in shades of brownish orange. Mesaite is monoclinic, P2/n, a = 9.146(2), b = 10.424(3), c = 15.532(4) Å, and β = 102.653(7)°. The strongest four diffraction lines in the powder diffraction pattern are (dobs, Iobs, hkl): (10.47, 100, 010), (2.881, 25, 132, -312, 033, 310), (3.568, 24, -114, -123, -213), (3.067, 17, -124, -132, -223). The composition of mesaite was determined by electron microprobe, and yielded an empirical formula of Mn5.32Ca0.56Zn0.31V5.96As0.04O33H23.61 24 on the basis of O = 33. The atomic arrangement of mesaite was solved and refined to R1 = 0.0600. The structure is formed of zigzag octahedral chains of edge-sharing Mn2+O6 octahedra. Oxygen atoms of the octahedra are shared with V2O7 groups, which link with adjacent octahedral chains to form {010} heteropolyhedral layers. The interlayer region contains Ca atoms and H2O groups. Each Ca bonds to two O6 atoms in the heteropolyhedral layer and to two fully occupied and six partially occupied O (H2O) sites in the interlayer, resulting in an effective Ca coordination of approximately seven. Zigzag, edge-sharing octahedral chains decorated with V2O7 or P2O7 groups are also known in the mineral fianelite and synthetic compounds, and are not limited to MnO6 and V2O7 units.
▪ Kampf, A.R., Nash, B.P., Marty, J., Hughes, J.M. (2017): Mesaite, CaMn2+5(V2O7)3·12H2O, a new vanadate mineral from the Packrat mine, near Gateway, Mesa County, Colorado, USA. Mineralogical Magazine, 81, 319–327.
Abstract:
Mesaite (IMA2015-069), ideally CaMn2+5(V2O7)3·12H2O, is a new mineral from the Packrat mine, Gateway district, Mesa County, Colorado. Crystals of mesaite occur as orangish red blades up to 0.1 mm long. The streak is light pinkish orange and the lustre is vitreous, transparent. Mesaite has a brittle tenacity, {010} perfect cleavage; fracture is irregular, and no parting was observed. The mineral has a Mohs hardness ca 2. The measured density of mesaite is 2.74(1) g cm-3. Mesaite is biaxial (-), α = 1.760(calc), β = 1.780(5), γ = 1.795(5) in white light; the measured 2V value = 81(2)°. Dispersion is strong, r < v, and pleochroism is present in shades of brownish orange. Mesaite is monoclinic, P2/n, a = 9.146(2), b = 10.424(3), c = 15.532(4) Å, and β = 102.653(7)°. The strongest four diffraction lines in the powder diffraction pattern are (dobs, Iobs, hkl): (10.47, 100, 010), (2.881, 25, 132, -312, 033, 310), (3.568, 24, -114, -123, -213), (3.067, 17, -124, -132, -223). The composition of mesaite was determined by electron microprobe, and yielded an empirical formula of Mn5.32Ca0.56Zn0.31V5.96As0.04O33H23.61 24 on the basis of O = 33. The atomic arrangement of mesaite was solved and refined to R1 = 0.0600. The structure is formed of zigzag octahedral chains of edge-sharing Mn2+O6 octahedra. Oxygen atoms of the octahedra are shared with V2O7 groups, which link with adjacent octahedral chains to form {010} heteropolyhedral layers. The interlayer region contains Ca atoms and H2O groups. Each Ca bonds to two O6 atoms in the heteropolyhedral layer and to two fully occupied and six partially occupied O (H2O) sites in the interlayer, resulting in an effective Ca coordination of approximately seven. Zigzag, edge-sharing octahedral chains decorated with V2O7 or P2O7 groups are also known in the mineral fianelite and synthetic compounds, and are not limited to MnO6 and V2O7 units.