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

Cassiterite – a Tin and Tantalum Source

Cassiterite

  • The name derives from the Greek kassiteros for tin
  • Cassiterite has been the chief tin ore throughout ancient history and remains the most important source of tin today
  • As often some of the tin atoms are substituted with iron, titanium, zirconium or tantalum, cassiterite, or to be precise, the smelting slag of SnO2, is in particular, also a source for tantalum
  • Belongs to the Rutile mineral group
  • Formula: SnO2
  • Space group: P42/mnm (No. 136)
  • Crystal system: tetragonal
  • Crystal class: 4/mmm
  • Lattice parameters: a = b = 4.7382(4) Å, c = 3.1871(1), αβγ = 90°

Picture: CarlesMillan – CC BY-SA 3.0


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).)

  • SnO6 octahedra (slightly distorted) (purple)
  • Oxygen (red)

For a 3D interactive version, see also here:

https://skfb.ly/6PzLY

Ref.:

Structural Studies of Rutile-Type Metal Dioxides
A. A. Bolzan, C. Fong, B. J. Kennedy and C. J. Howard
Acta Cryst. B 1997, 53, 373-380
https://doi.org/10.1107/S0108768197001468

 

Ice V and XIII

Ice V and XIII

  • can be formed by slowly cooling liquid water at ~ 5 kbar from 20 °C to – 20 °C
  • density: 1.23 g/cm3

Structural features

  • Ice V is a proton-disordered phase
  • the analogous proton-ordered phase is Ice XIII
  • all water molecules are hydrogen-bonded to four others, two as donor and two as acceptor, at distances of 2.76 to 2.87 Å
  • the coordination tetrahedra are largely distorted with angles ranging from 84 to 128°.
  • Ice V contains 4,- 5-, 6-, and 7-membered rings
  • Space group: A2/a (No. 15)
  • Crystal system: monoclinic
  • Lattice parameters:
    • a = 9.22(2) Å, b = 7.54(1) Å, c = 10.35(2) Å
    • α = γ = 90°, β =109.2(2)°
    • 28 molecules per unit cell

 Here, you can download the CIF.

Literature:

[1] B. Kamb, A. Prakash, C. Knobler, Structure of Ice V, Acta Cryst. 1967, 22, 706-715. DOI: 10.1107/S0365110X67001409

Atomistic structure figures were created with

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