Monthly Archives: November 2016

The Beauty 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°


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


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


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


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


Picture: Red Beryl, Rob Lavinsky, – 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).)

  • 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


  • 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°


Picture: Didier Descouens – CC BY-SA 4.0

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


  • 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


  • 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°


Picture: Rob Lavinsky, – CC BY-SA 3.0

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


  • 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”…


…is now available on Amazon:

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

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…


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

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

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.

Yet another mineral – Today: Baryte


  • named after the greek word for heavy (the density is relatively high
    with 4.5 g/cm3)
  • Formula: BaSO4
  • Space group: Pnma (No. 62)
  • Crystal system: orthorhombic
  • Crystal class: mmm
  • Lattice parameters: a = 8.88 Å, b = 5.46 Å, c = 7.16 Å, α = β = γ =  90°


Picture: Carlesmillan – CC BY-SA 3.0

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


slightly distorted SO42- tetrahedra (yellow), Ba2+ ions (green), which are surrounded by 12 oxygen atoms