Tag Archives: crystallography

Jarosite – Indicator of (liquid) water on Mars

Jarosite

  • Named after its type locality, Barranco del Jaroso in the Sierra Almagrera (near Los Lobos, Cuevas del Almanzora, Almería, Spain)
  • In 2004 the Mars Exploration Rover – B found Jarosite on Mars. Because on Earth Jarosite is only formed in liquid water, this finding strongly indicates that Mars once possessed large amounts of liquid water.
  • Formula: KFe3(OH)6(SO4)2
  • Space group: R-3m (No. 166)
  • Crystal system: trigonal
  • Crystal class: -3m
  • Lattice parameters: a = b = 7.304 Å, c = 17.268 Å, αβ = 90°, γ = 120°

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).)

  • KO12 only very slightly distorted icosahedra (purple)
  • FeO6 octahedra (blue)
  • SO4 tetrahedra (yellow)
  • Oxygen (red)

For a 3D interactive version, see here:

https://skfb.ly/6pGuY

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Hercynite – A ferro spinel

Hercynite

  • Named after the latin name Silva Hercynia of the Bohemian Forest, where this mineral was first found
  • it is a ferro spinel
  • Formula: FeAl2O4
  • Space group: Fd-3m (No. 227)
  • Crystal system: cubic
  • Crystal class: m-3m
  • Lattice parameters: a = b = c = 8.1458 Å, α = β =  γ = 90°

Picture: CC BY-SA 3.0 nl | Fred Kruijen | http://www.mindat.org/photo-73060.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).)

  • FeO4 tetrahedra (orange)
  • Al (blue), octahedral oxide coordination environment
  • Oxygen (red)

For a 3D interactive version, see here:

https://skfb.ly/66QEE

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

Orange-Red like Saffron: Crocoite

Crocoite

  • The name crocoite comes from the Greek “krokos” = saffron, alluding to the saffron-orange color of its powder
  • Formula: PbCrO4
  • Space group: P21/n (No. 14)
  • Crystal system: monoclinic
  • Crystal class: 2/m
  • Lattice parameters: a = 7.127 Å, b = 7.438 Å, c = 6.799 Å, α = 90°, β = 102.43°, γ = 90°

crocoite-360746_pd

Picture: Juergen Merzhttp://www.mindat.org/photo-360746.html
(This image has been released to the public domain.)


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).)

crocoite

View along the a axis.

Gray: Pb, red: O, orange: CrO4 tetrahedra

The official gem of California: Benitoite

Benitoite

  • named after its type locality San Benito County (California)
  • it is the official state gem of California
  • Formula: BaTiSi3O9
  • Space group: P-6c2 (No. 188)
  • Crystal system: hexagonal
  • Crystal class: -6m2
  • Lattice parameters: a = b =  6.641 Å, c = 9.7579 Å, α = β = 90°, γ  120°

benitoite_hd

Picture: Didier Descouens – CC BY-SA 4.0


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

benitoite

  • Ba: green, Ti: lightblue, Si: orange, O: red
  • TiO6 octahedra, SiO4 tetrahedra
  • three corner-connected SiO4 tetrahedra build a ring

A rare grass-green mineral: Bayldonite

Bayldonite

  • named after its discoverer, the British physicist John Balydon
  • Formula: PbCu3(AsO4)2(OH)2
  • Space group: C2/c (No. 15)
  • Crystal system: monoclinic
  • Crystal class: 2/m
  • Lattice parameters: a = 10.15 Å, b = 5.89 Å, c = 14.08 Å, β  106.1°

bayldonite-173845

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

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

bayldonite

  • Cu: blue, As: green, Pb: black, O: red, H: white
  • elongated CuO6 octahedra
  • AsO4 tetrahedra
  • Pb surrounded by 7 oxygen atoms

Textbook published / Lehrbuch veröffentlich

Dear readers of my blog,

I am very pleased to announce that my introductory textbook on crystallography “Faszination Kristalle und Symmetrie”…

springer_lehrbuch_cover

…is now available on Amazon:

https://www.amazon.de/Faszination-Kristalle-Symmetrie-Kristallographie-Studienb%C3%BCcher/dp/3658095806

The electronic (ePub, PDF) version is available on the publishers site at Springer:

http://www.springer.com/de/book/9783658095802

There are also some additional electronic resources available, which are gathered on this particular webpage.

This first edition is published only in German, however, it is not excluded that further editions will be also available in English; that is, of course, the decision of the publisher.

=============================================

Liebe Leserinnen und Leser dieses Blogs,

ich freue mich, ankündigen zu können, dass mein kleines einführendes Buch zur Kristallographie…

springer_lehrbuch_cover

soeben erschienen ist und z.B. über Amazon bestellbar ist:

https://www.amazon.de/Faszination-Kristalle-Symmetrie-Kristallographie-Studienb%C3%BCcher/dp/3658095806

Das eBook ist in zwei verschiedenen Formaten (ePub, PDF) auf der Springer-Verlagsseite verfügbar:

http://www.springer.com/de/book/9783658095802

Desweiteren sind auf dieser Webseite einige zusätzliche elektronische Ressourcen zusammengetragen, z.B. Bastelbögen für Kristallmodelle aus Papier, einige Animationen und Kristallstrukturdateien (CIF- und VESTA-Dateien) von einigen Mineralen und anderen chemischen Verbindungen.

Diese erste Auflage ist nur auf Deutsch erschienen, aber es ist nicht ausgeschlossen, dass künftige Auflagen auch ins Englische übersetzt werden.