Tag Archives: Crystal structure

Mellite

Mellite

  • Also known as honeystone due to its often honey-yellow color
  • Mellite is the aluminium salt of mellitic acid, i.e. benzene hexacarboxylic acid
  • Formula: Al2C6(COO)6 · 16 H2O
  • Space group: I41/acd (No. 142)
  • Crystal system: tetragonal
  • Crystal class: 4/mmm
  • Lattice parameters: a = b = 15.553 Å, c = 23.110 Å, α = β = γ = 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).)

 

 

  • AlO6 octahedra (blue)
  • Oxygen (red)
  • Carbon (black)
  • Hydrogen (white)

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

https://skfb.ly/6rSSR

 

Lavendulan

Lavendulan

  • The colour varies between turquoise and lavender, often also electric blue specimens can be found (see the picture below)
  • Formula: NaCaCu5(AsO4)4Cl · 5 H2O
  • Space group: P21/n (No. 14)
  • Crystal system: monoclinic
  • Crystal class: 2/m
  • Lattice parameters: a =  10.011, b = 19.478 Å, c = 10.056 Å, α = 90° β = 90.37°, γ = 90°

Picture: CC BY-SA 3.0 | Christian Rewitzer


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).)

  • CuO5 and CuO4Cl tetragonal pyramids (blue)
  • CaO7 polyhedra (light blue)
  • NaO6 distorted trigonal prismatic units (yellow)
  • AsO4 tetrahedra (green)
  • Chlorine (bright green)
  • Oxygen (red)
  • Oxygen of water molecules (dark red)

For a 3D interactive version, see here:

https://skfb.ly/6qsoV

Keyite – A Complex Copper-Zinc-Cadmium Arsenate

Keyite

  • Named after the mineral dealer Charley Key, who discovered some tiny blue crystals of this mineral on a sample of green Adamite
  • Formula: Cu3(Zn,Cd)4Cd2(AsO4)6· 2 H2O
  • Space group: I2/a (No. 15)
  • Crystal system: monoclinic
  • Crystal class: 2/m
  • Lattice parameters: a = 11.654 Å, b = 12.780 Å, c = 6.268 Å, αγ = 90°, β = 99.11°

Picture: CC BY-SA 3.0 | Christian Rewitzer


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).)

  • CuO4 square-planar units (blue)
  • CuO6 distorted octahedra (blue)
  • CdO6 distorted trigonal prismatic units (pink)
  • AsO4 distorted tetrahedra (green)
  • Oxygen (red)
  • Oxygen of water molecules (black(

For a 3D interactive version, see here:

https://skfb.ly/67tQD

Ilmenite – the titanium dioxide source

Ilmenite

  • Named after it’s type locality, the Ilmensky Mountais in the Southern Urals (Russia)
  • Most important titanium mineral; it is predominantly mined for titanium dioxide production
  • Formula: FeTiO3
  • Space group: R-3 (No. 148)
  • Crystal system: trigonal
  • Crystal class: -3
  • Lattice parameters: a = b = 5.0884 Å, c = 14.0855 Å, αβ = 90°, γ = 120°

Picture by Modris Baum (Public Domain)


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).)

  • FeO6 distorted octahedra (brown)
  • TiO6 distorted octahedra (blue)
  • Oxygen (red)
  • The structure can be derived from the corundum (Al2O3) type: in corundum all cations are identical but in ilmenite Fe2+ and Ti4+ ions occupy alternating layers perpendicular to the c axis
  • Within the alternating layers the FeO6 / TiO6 octahedra are edge-connected to give six-membered rings (the centre of the hexagons are unoccupied)

For a 3D interactive version, see here:

https://skfb.ly/6ps9E

Gottlobite: The “Thank God” Mineral

Gottlobite

  • Literally translated from German the meaning is “Thank God”; it is named after its type locality, the hill Gottlob (573 m) near Friedrichroda, Thuringia, Germany
  • Known only since 1996
  • Formula: CaMg(VO4,AsO4)(OH)
  • Space group: P212121 (No. 19)
  • Crystal system: orthorhombic
  • Crystal class: 222
  • Lattice parameters: a = 7.501 Å, b = 9.010 Å, c = 5.941 Å, α = β =  γ = 90°

gottlobite

Picture: CC BY-SA 3.0 de – Thomas Witzkehttp://tw.strahlen.org/typloc/gottlobit.html


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).)

gottlobite

View along the c axis.

  • MgO6 octahedra (orange)
  • AsO4/VO4 tetrahedra (purple)
  • Ca (blue)
  • Oxygen (red)

For a 3D interactive version, see here:

https://skfb.ly/6nBSF

Freieslebenite

Freieslebenite

  • Named after the mine commissioner of Saxony (Germany) Johann Carl Freiesleben
  • Formula: AgPbSbS3
  • Space group: P21/a (No. 14)
  • Crystal system: monoclinic
  • Crystal class: 2/m
  • Lattice parameters: a = 7.518 Å, b = 12.809 Å, c = 5.940 Å, α = 90°, β = 92.25°, γ = 90°

freieslebenite-169965

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).)

freieslebenite

View along the c axis.

  • AgS3 (ditorted) trigonal-planar coordination environment (gray)
  • SbS3 trigonal-pyramidal coordination environment (green)
  • PbS6 distorted octahedra (orange)

Dioptase: emerald-green and visible cleavage planes

Dioptase

  • The name dioptase comes from the Greek words “dia” (= through) and “optos” (= visible), alluding to the visible cleavage planes inside the often highly transparent or translucent crystals
  • Formula: CuSiO3 · H2O
  • Space group: R-3 (No. 148)
  • Crystal system: trigonal
  • Crystal class: -3
  • Lattice parameters: a = b = 14.566 Å, c = 7.778 Å, αβ = 90°, γ = 120°

Dioptase Tsumeb

Dioptase Tsumeb

Picture: Didier Descouens – 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).)

dioptase

View along the c axis.

  • six SiO4 tetrahedra (orange) are corner-connected to build a ring, so the mineral belongs to the cyclo silicates
  • the copper atoms (blue) are octahedrally coordinated by six oxygen atoms (red), four of them are oxygens involved in SiO4 tetrahedra and they occupy the equatorial positions of the CuO6 octahedra and two of them are oxygen atoms of water molecules, which occupy the axial positions of the CuO6 octahedra
  • the CuO6 octahedra are edge-connected and build a continuous 3D net