Tag Archives: Crystal structure

Stibnite – a black make-up mineral

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, = 3.8363 Å, c = 11.2285 Å, αβ = 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


 

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Abelsonite – a chemofossil

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

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/(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

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

Ice IV – a remarkable self-interpenetrating structure

Ice IV (Ice four)

  • metastable in the phase space between Ice III, Ice V and Ice VI (see orange circle in the Figure above)
  • may be formed from high-density amorphous ice by slow heating from 145 K and a constant pressure of 8 kbar
  • calc. density at 110 K and 1 bar = 1.27 g/cm3

Structural features

  • proton-disordered phase
  • all water molecules are hydrogen-bonded to four others, two as donor and two as acceptor
  • exclusively 6-membered rings (two types, one almost flat, the other more puckered)
  • the most striking structural feature is that Ice IV builds a self-interpenetrating structure, but this does not consists of two independent networks but of only one net: two water molecules (shown in blue in the following Figure) bonded by H-bonds are oriented perpendicular and are running through the center of the almost flat 6-membered rings:

  • Space group: R-3c (No. 167)
  • Crystal system: trigonal
  • Lattice parameters:
    • a = b = 8.72922 Å, c = 17.06581 Å
    • α = β = 90°, γ =120°

 Here, you can download the CIF.

Literature:

[1] H. Engelhardt and B. Kamb, Structure of ice IV, a metastable high-pressure phase, Journal of Chemical Physics 1981, 75, 5887-5899. DOI: 10.1063/1.442040

[2] C. G. Salzmann, I. Kohl, T. Loerting, E. Mayer and A. Hallbrucker, Raman spectroscopic study on hydrogen-bonding in recovered ice IV, Journal of Physical Chemistry B 2003, 107, 2802-2807. DOI: 10.1021/jp021534k

 

[Atomistic structure figures 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).

and

CrystalMaker®.]

Ice III and IX

Ice III and IX (Ice three and Ice nine)

  • Ice III can be formed from liquid water at 300 MPa (3000 bar) by lowering the temperature to approx. 250 K.
  • The relative permittivity is very high (~ 117)
  • Density: 1.16 g/cm3

Structural features

  • Ice III is also called Keatite Ice, because the oxygen atoms are located at analogous positions of the silicon atoms in the SiO2 phase Keatite.
  • Ice IX is the proton-ordered form of Ice III.
  • The tetrahedral environment of the water molecules are considerably distorted.
  • Interestingly, there are no 6-membered rings present anymore, but 5, 7, and 8 –membered rings instead. The 5-membered rings can be best seen if you look along the a or b direction:

 

    • Two-third of the water molecules are forming 41 helices/screws running along the c axis, which means that Ice III is chiral! The other water molecules connect these helices and are forming a 21 helix.

 

  • Space group: P41212 (No. 92)
  • Crystal system: tetragonal
  • Lattice parameters:
    • a = b = 6.73(1) Å, c = 6.83(1) Å
    • α = β = γ = 90°

 

 Here, you can download the CIF.

[Atomic structure figures 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).

and

CrystalMaker®.

Celestial Celestine

Celestine

  • named from the Latin word caelestis meaning celestial, which in turn is derived from the Latin word caelum meaning sky or heaven because of its often soft blue color
  • pure Celestine is colourless
  • due to lattice defects in Celestine, colour centres are created which give the crystal its characteristic bluish colour
  • these centers are often additionally stabilized by the presence of pottasium ions
  • heating to over 200 °C “cures” these lattice defects and the mineral loses its color
  • radiation with X-rays creates new or more lattice defects and the color returns or can be intensified.
  • Formula: SrSO4
  • Space group: Pnma (No. 62)
  • Crystal system: orthorhombic
  • Crystal class: mmm
  • Lattice parameters:  a = 8.360 Å, b = 5.352 Å, c = 6.858 Å, αβγ = 90°

Picture: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0


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).)

  • SO4 tetrahedra (yellow)
  • SrO8 polyhedra (green)
  • Oxygen (red)

For a 3D interactive version, see here:

https://skfb.ly/6zG6R