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

Cinnabar: Red as dragon blood and optically active

Cinnabar

  • probably named after the Persian word for dragon blood because of its characteristic red colour
  • used since ancient times as a pigment
  • Formula: HgS
  • Space group: P3121 (No. 152) or P3221 (No. 154)
  • Crystal system: trigonal
  • Crystal class: 32
  • Lattice parameters: a = b = 4.1347(6) Å, c = 9.4451(3) Å, αβ = 90°, γ = 120°

Modified by CombineZP

Modified by CombineZP

Picture: JJ Harrison (jjharrison89@facebook.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).)

cinnabar_01

View along the c axis.

cinnabar_02

View along the a axis.

  • the crystals structure is characteristic of chains with alternating sulfur and mercury atoms, which form helices with the helix axis running parallel to the c axis.
  • These helices are also the reason why crystals of cinnarbar are optically active (see: A.M. Glazer, K. Stadnicka, “On the origin of optical activity in crystal structures”. J. Appl. Cryst. 19 (2), 1986, 108–122. doi:10.1107/S0021889886089823

Bornite: Why order sometimes means less symmetry

Bornite

  • named after the Austrian mineralogist Ignaz von Born
  • also known as peacock ore because in air this mineral forms very quickly an iridescent coverage on its surface
  • Formula: Cu5FeS4
  • Space group: Pbca (No. 61)
  • Crystal system: orthorhombic
  • Crystal class: mmm
  • Lattice parameters: a = 10.950 Å, b = 21.862 Å, c = 10.950, αβγ = 90°

bornite_irocks

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


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

bornite

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

  • yellow: Sulfur, blue: Copper, orange: Iron
  • The structure is based on a cubic-closest packing of sulfide ions; the copper and iron ions are located in 3/4 of the tetrahedral voids of the packing. At temperatures above 228 °C the cations are completely randomly distributed over these sites (the crystallographer names it disorder), forming a genuine (isometric) cubic phase, but in the low temperature modification the cations are more ordered, which is accompanied with the symmetry reduction to the orthorhombic crystal system

The Beauty Beryl

Beryl

  • named after the latin word beryllus or greek word beryllos, respectively, which is referred to “precious blue-green color-of-sea water stone”
  • the first lenses were made of beryl, as glass could not be made clear enough; this is the origin of the German word for glasses, i.e. “Brille”
  • there are important varieties, namely the blue Aquamarine (Fe2+ impurities), the Green Emerald (Cr3+ impurities), the Golden Beryl (Fe3+ impurities), the Pink or Rose Beryl named Morganite (after the financier J.P. Morgan, containing Mn2+ impurities), and the Red beryl
  • Formula: Al2Be3Si6O18
  • Space group: P6/mmc (No. 192)
  • Crystal system: hexagonal
  • Crystal class: 6/mmm
  • Lattice parameters: a = b =  9.219 Å, c = 9.198 Å, α = β = 90°, γ  120°

beryl-aquamarin_118278

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


beryl-quartz-emerald-zambia-33mm_0885

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


beryl-gold_beryl_tt64a

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


beryl-albite_morganit-197426

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


beryl-red-beryl-196800

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


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

beryl

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

  • yellow: SiO4 tetrahedra, six tetrahedra are corner-connected to form a ring
  • green: distorted BeO4 tetrahedra
  • blue: slightly distorted AlO6 octahedra

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.