Tag Archives: Crystal structure

Pentlandite – the most important nickel ore

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Pentlandite

  • Named after the Irish natural historian, J. B. Pentland (1797-1873)
  • Pentlandite is the most important nickel ore
  • Formula: (Fe,Ni)9S8
  • Space group: Fm-3m (No. 225)
  • Crystal system: cubic
  • Crystal class: m-3m
  • Lattice parameters: a = b = c = 10.1075(1) Å, α = β = γ = 90°

Picture by: John Sobolewski (JSS) – http://www.mindat.org/photo-192760.html, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=9578696

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).)

  • For both metal cation positions there is a complete disorder between Ni and Fe.
  • There are two distinct coordination environments; octahedrally coordinated metals at the center and all edge centers and tetrahedrally coordinated metals for the others.
  • Eight tetrahedra each form edge-connected Fe/Ni8(µ-S)6S8 motifs, that means cubes of metal ions with six face-capping and eight terminal S atom. If we take now these cubes and octahedra as building blocks they form a NaCl-like structure.
  • Fe/NiS4 tetrahedra (blue)
  • Fe/NiS6 octahedra (orange)
  • Fe (brown)
  • Ni (green)

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

https://skfb.ly/6UPTq

References:

[1] Tenailleau, C., Etschmann, B., Ibberson, R. M. & Pring, A.
A neutron powder diffraction study of Fe and Ni distributions in synthetic pentlandite and violarite using 60Ni isotope.
Am. Mineral. 91, 1442–1447 (2006)

[2] Stacey, T. E., Borg, C. K. H., Zavalij, P. J. & Rodriguez, E. E.
Magnetically stabilized Fe8(µ-S)6S8 clusters in Ba6Fe25S27.
Dalton Trans. 43, 14612–14624 (2014)

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Wulfenite

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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/a (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

Antarcticite

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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

Ice V and XIII

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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).

Vermiculite – Mineral of the Year 2019 in Austria

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Vermiculite

  • The mineral was first described in 1824 by Thomas H. Webb. Due to the property of the mineral to expand into worm-like formations when heated to 200 to 300 °C in the direction of the crystallographic c-axis, Webb named it after the Latin word “vermiculor” for “worm breeder”.
  • On the occasion of the 195th anniversary of its discovery and due to its great importance as an industrial mineral, vermiculite was voted “Mineral of the Year” in Austria in 2019.
  • Formula: Mg0,7(Mg,Fe,Al)6(Si,Al)8O20(OH)4 · 8 H2O
  • Space group: C2/c (No. 15)
  • Crystal system: monoclinic
  • Crystal class: 2/m
  • Lattice parameters: a = 5.349 Å, b = 9.255 Å, c = 28.89, α = γ = 90°, β = 97.12°

Picture: CC BY-SA 3.0 Leon Hupperichs

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).)

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

https://skfb.ly/6OKvO

Tetrahedrite

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Tetrahedrite

  • named after its common outer shape – a tetrahedron
  • because of its relative high copper content it is also a (minor) ore of copper
  • Formula: Cu12[S|(SbS3)4]
  • Space group: I-43m (No. 217)
  • Crystal system: cubic
  • Crystal class: -43m
  • Lattice parameters: a = b =  c = 10.448 Å, α = β = γ  = 90°

Picture: Carles Millan – http://www.mindat.org/photo-176605.html  | 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).)

  • SbS3 pyramids (purple)
  • CuS3 trigonal planar coordination (cyan)
  • CuS4 tetrahedra (blue)
  • Copper (blue)
  • Sulfur (yellow)
  • Antimony (purple)

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

https://skfb.ly/6Or6R

Stibnite – a black make-up mineral

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Stibnite

  • Synonym: Antimonite
  • The mineral has been known since ancient times and was used as a paste with fat as black make-up powder to color eyelids and eyebrows. In Arabic culture, dark eye rims are regarded as the ideal of beauty and at the same time as a magical repellent.
  • Formula: Sb2S3
  • Space group: Pnma (No. 62)
  • Crystal system: orthorhombic
  • Crystal class: mmm
  • Lattice parameters: a = 11.3107 Å, b = 3.8363 Å, c = 11.2285 Å, α = β = γ = 90°

Picture: DerHexer, Wikimedia Commons, CC BY-SA 4.0

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).)

  • SbS5 tetragonal pyramids (purple)

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

https://skfb.ly/6JoCM

 

Abelsonite – a chemofossil

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Abelsonite

  • Discovered only in 1969 (by the way the year of birth of the author of this blog) by Lawrence C. Trudell while he was exploring the Green River Formation (Utah, USA) for an oil shale project
  • Named after Philip H. Abelson (1913–2004), a long-time editor of the journal Science, for his pioneering work in organic geochemistry
  • Abelsonite is formed as a secondary mineral (and is one of the few organic minerals)  on oil shale surfaces by conversion of chlorophyll – therefore, it is called a chemofossil (a fossil that consists only of chemicals remaining from the decomposition of a living organism)
  • Abelsonite is the only known naturally occurring crystalline porphyrin derivative
  • Formula: NiC31H34N4
  • Space group: P-1 (No. 2)
  • Crystal system: triclinic
  • Crystal class: -1
  • Lattice parameters: a = 8.4416 Å, b = 10.8919 Å, c = 7.2749, α = 90.465°, β =113.158°,  γ = 78.080°

Picture: CC BY-SA 3.0 Thomas Witzke – http://tw.strahlen.org/fotoatlas1/abelsonite_foto.html

Crystal structure (click on the picture to download the CIF):

  • Ni: green, N: blue, C: gray, H: white
  • Note: Although a single Ni porphyrin molecule does not possess -1 symmetry, matching ethyl groups at roughly opposite ends of the molecule enable orientational disorder, in which molecules can randomly adopt one of two different orientations while still stacking in the same manner. The aggregate of these two random orientations produces an overall symmetry of P-1.
  • Reference: Crystal structure of abelsonite, the only known crystalline geoporphyrin
    Daniel R. Hummer, Bruce C. Noll, Robert M. Hazen, Robert T. Downs
    American Mineralogist (2017) 102 (5): 1129-1132.
    https://doi.org/10.2138/am-2017-5927

Sartorite

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Sartorite

  • Named after Wolfgang Sartorius von Waltershausen (1809 – 1876) Professor of Mineralogy, University of Göttingen, Germany. He was the first who described the mineral.
  • Formula: PbAs2S4
  • Space group: P21/n (No. 14)
  • Crystal system: monoclinic
  • Crystal class: 2/m
  • Lattice parameters: a = 19.62 Å, b = 7.89 Å, c = 4.19 Å, α = γ = 90°,  β = 90° (!)

Picture: Rob Lavinsky, iRocks.com – 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).)

  • PbS9 polyhedra (gray)
  • AsS3 trigonal pyramids (green)
  • Sulfur (yellow)

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

https://skfb.ly/6IYWO

Portlandite – basis for a very important building material

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Portlandite

  • Named portlandite because it is a common product of hydration of portland cement
  • Formula: Ca(OH)2
  • Space group: P-3m1 (No. 164)
  • Crystal system: trigonal
  • Crystal class: -3 2/m
  • Lattice parameters: a = b = 3.5918 Å, c = 4.9063 Å, α = β = 90°, γ = 120°

Picture (public domain): SEM image of fractured hardened cement paste, showing plates of calcium hydroxide and needles of ettringite

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).)

  • CaO6 octahedra (blue)
  • Oxygen (red)
  • Hydrogen (white)

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

https://skfb.ly/6ItSG