Monthly Archives: January 2020

Spangolite – A Pyroelectric Copper Sulfate Sheet Mineral

Spangolite

  • Named in honour of Norman Spang (1841–1922), a mineral collector from Pennsylvania, USA; for details, see here.
  • Spangolite is pyroelectric
  • Formula: Cu6Al(SO4)(OH)12Cl · 3 H2O
  • Space group: P31(No. 159)
  • Crystal system: trigonal
  • Crystal class: 3m
  • Lattice parameters: a = b = 8.254(4) Å, c = 14.354(8) Å, α = β = 90°, γ = 120°

Picture: Christian Rewitzer, CC BY-SA 3.0
https://commons.wikimedia.org/w/index.php?curid=14865917


Crystal structure (click on the picture to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,”J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • CuO6 distorted octahedra (blue)
  • AlO6 octahedra (orange)
  • SOtetrahedra (yellow)
  • Oxygen (red)
  • Chlorine (green)
  • Hydrogen (white)

For a 3D interactive version on sketchfab, see here:

https://skfb.ly/6Q6U7

References:

[1] Spangolite
H. A. Miers
Mineralogical Magazine 1894, 10, 273-277

DOI: 10.1180/minmag.1894.010.48.02

[2] The Crystal Structure of Spangolite, a Complex Copper Sulfate Sheet Mineral
F.C. Hawthorne, M. Kimata, R.K. Eby
American Mineralogist 1993, 78 (5-6), 649-652.

Suzukiite – polymorphic to Bavsiite

Suzukiite

  • Named in honor of Jun Suzuki, a professor of mineralogy and petrology, at the Hokkaido University, Sapporo (Japan).
  • Suzukiite belongs to the inosilicates (chain silicates) and is polymorphic to Bavsiite, which is tetragonal.
  • Formula: BaVSi2O7
  • Space group: Cmcm (No. 63)
  • Crystal system: orthorhombic
  • Crystal class: mmm
  • Lattice parameters: a = 5.3546(16), b = 15.249(5) Å, c = 7.094(2) Å, α = β = γ = 90°

Picture: D. Nishio-Hamane – CC BY-NC-SA 2.0


Crystal structure (click on the picture to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,”J. Appl. Crystallogr., 44, 1272-1276 (2011).)

 

  • BaO10 polyhedra (not shown as polyhedra, Ba green)
  • SiO4 tetrahedra (yellow)
  • VO5 square pyramids (purple)
  • Oxygen (red)

For a 3D interactive version on sketchfab, see here:

https://skfb.ly/6Q6GC

Reference:
Crystal Structure of Suzukiite from the Mogurazawa Mine, Gunma Prefecture, Japan,
M. Ito, S. Matsubara, K. Yokoyama, K. Momma, R. Miyawaki, I. Nakai, A. Kato
Journal of Mineralogical and Petrological Sciences 2014, 109, 222-227

DOI: 10.2465/jmps.140520

Bavsiite – A mineral containing Ba, V, Si,…

Bavsiite

  • Named for the constituting elements Barium, Vanadium and Silicon.
  • Bavsiite is polymorphic to Suzukiite, BaVSi2O7, which is orthorhombic.
  • Formula: Ba2V2O2[Si4O12]
  • Space group: I4/(No. 87)
  • Crystal system: tetragonal
  • Crystal class: 4/m
  • Lattice parameters: a = b = 7.043(1) Å, c = 11.444(2) Å, α = β = γ = 90°

Crystal structure (click on the picture to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,”J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • BaO12 polyhedra (not shown as polyhedra, Ba green)
  • SiO4 tetraedra (yellow) building single four-rings
  • VO5 square pyramids (blue)
  • Oxygen (red)

For a 3D interactive version on sketchfab, see here:

https://skfb.ly/6PYVA

Reference:
Bavsiite, Ba2V2O2[Si4O12], mineral data and crystal structure
H.-P. Bojar, F. Walter, J. Baumgartner
Mineralogical Magazine 2019, 83, 821-827

DOI: 10.1180/mgm.2019.59

Wulfenite

Wulfenite

  • Named in honour of Franz Xavier Wulfen (1728–1805), Austrian–German Jesuit, who wrote a monograph on the lead ores of Bleiberg, Austria.
  • Wulfenite was voted “Mineral of the Year” in Austria in 2020.
  • In its pure form wulfenite is colorless; the often yellow to red colour is most probably due to trace amounts of chromium substituting Mo.
  • Formula: PbMoO4
  • Space group: I41/(No. 88)
  • Crystal system: tetragonal
  • Crystal class: 4/m
  • Lattice parameters: a = b = 5.434 Å, c = 12.107 Å, α = β = γ = 90°

Modified by CombineZP

Picture: Didier Descouens – CC BY-SA 4.0
https://commons.wikimedia.org/w/index.php?curid=12426342


Crystal structure (click on the picture to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,”J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • PbO8 coordination environment
  • MoO4 tetrahedra (blue)
  • Pb (black)
  • Oxygen (red)

For a 3D interactive version on sketchfab, see here:

https://skfb.ly/6PW6U

Reference:
Natural wulfenite: structural refinement by single-crystal X-ray diffraction
C. Lugli, L. Medici, D. Saccardo,
Neues Jahrbuch fur Mineralogie, Monatshefte 1999, 6, 281-288

Vanadinite – the most important vanadium source

Vanadinite

  • Named for its vanadium content
  • Vanadinite is the most important source of vanadium and finds application as V2O5 in the famous contact process (production of sulfuric acid) and in alloys for chromium-vanadium steel (typically the content is below 0.2 %)
  • Formula: Pb5(VO4)3Cl
  • Space group: P63/(No. 176)
  • Crystal system: hexagonal
  • Crystal class: 6/m
  • Lattice parameters: a = b = 10.299(2) Å, c = 7.308(1) Å, α = β = 90°, γ = 120°

Picture: Didier Descouens – CC BY-SA 4.0
https://commons.wikimedia.org/w/index.php?curid=12436369


Crystal structure (click on the picture to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,”J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • PbO9 irregular polyhedra (black)
  • PbO7 capped trigonal prisms (blue)
  • VO4 tetrahedra (purple)
  • Oxygen (red)
  • Chlorine (green)

For a 3D interactive version on sketchfab, see here:

https://skfb.ly/6PT8q

Reference:
Crystal structure of vanadinite: refinement of anisotropic displacement parameters
F. Laufek et al.
J. Czech Geol. Soc. 2006, 51, 271-275

DOI: 10.3190/JCGS.999

Antarcticite

Antarcticite

  • named after the type locality – the Don Juan Pond in Antarctica
  • Antarcticite is very hygroscopic and is formed only in very arid regions and precipitates only from highly saline brines
  • Formula: CaCl2  · 6 H2O
  • Space group: P321
  • Crystal system: trigonal
  • Crystal class: 32
  • Lattice parameters: a = b =  7.8759(2) Å, c = 3.9545(2) Å, α = β = 90°, γ  120°

Crystal structure (click on the pictures to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,” J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • every Ca ion is surrounded by nine water molecules
  • the CaO9 polyhedra (blue) are face-connected and stacked along the c axis
  • these faces are made up of three water molecules  acting as bridging ligands between two Ca ions
  • every Cl anion is involved in 6 H-bonds (dotted lines)
  • Oxygen (red)
  • Chlorine (green)
  • Hydrogen (white)

For a 3D interactive version, see here:

https://skfb.ly/6PJXV

Refs:

[1] T. Torii, J. Ossaka, Science 1965, 149, 975-977.
DOI: 10.1126/science.149.3687.975

[2] P. A. Agron, W. R. Busing, Acta Crystallogr. C 1986, 42, 141-143.
DOI: 10.1107/S0108270186097007

Troilite – most frequently from outer space

Troilite

  • Troilite occurs at only very few places on earth but  is abundant on our moon and also on Mars. The most frequent occurrences on earth are within meteorites.
  • Troilite was named after Domenico Troili who collected and examined samples of a meteorite that fell on earth in Albareto (near Parma) in 1766.
  • Formula: FeS
  • Troilite is the iron-rich endmember of the pyrrhotite group, the iron-deficient variant of FeS with the formula Fe(1-x)S (x = 0 to 0.2).
  • Space group: P-62(No. 190)
  • Crystal system: hexagonal
  • Crystal class: -6m2
  • Lattice parameters: a = b = 5.962(2) Å, c = 11.750(3) Å, α = β = 90°, γ = 120°

A section of the meteorite Sikhote Alin that has Troilite inclusions.

Picture: André Knöfel, CC BY-SA 3.0 de
https://commons.wikimedia.org/w/index.php?curid=7803661


Crystal structure (click on the picture to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,”J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • Although it is a stoichiometric 1:1 compound the Fe (brown) and S (yellow) atoms do have different coordination environments:
    • FeS6 (distorted) octahedra
    • SFe6 (distorted) trigonal prisms
  • This is analogous to NiAs; however, in Troilite the unit cell represents a superstructure of the simple NiAs-type structure (P63/mmc) based on small displacements of the Fe and S atoms from their ideal positions leading to an overall reduced symmetry (P-62c).
  • The hexagonal close-packed sulfur framework remains essentially the same.

For a 3D interactive version on sketchfab, see here:

https://skfb.ly/6PHBS

Reference:
Lunar Troilite: Crystallography
H. T. Evans Jr
Science 1970, 167, 621-623

DOI: 10.1126/science.167.3918.621