Tag Archives: crystals

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

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)

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

Selected Minerals – Today: Azurite

Azurite

  • named after the color azure, a variation of blue that is often
    described as the color of the sky
  • one of the two basic copper(II) carbonate minerals, the other being malachite
  • Formula: Cu3(CO3)2(OH)2
  • Space group: P21/c (No. 14)
  • Crystal system: monoclinic
  • Crystal class: 2/m
  • Lattice parameters: a = 5.01 Å, b = 5.58 Å, c = 10.35 Å, α = 90°, β = 92.4°, γ = 90°

azurite-155874

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


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

azurite

CO3 triangles (black), CuO5 tetragonal pyramids (yellow)

Chapter 5 now on YouTube

Chapter 5 released!

Dear all,

today Chapter 5 of our course has been released on YouTube!

In this chapter we will practise the handling with the International Tables a little further. But in contrast to staring only at circles and commas we will additionally look at real world crystals and some of their symmetry and physical properties.

And you can be curious about the story of one of the most thrilling scientific discoveries of the last century: the discovery of quasicrystals by Dan Shechtman.

Enjoy!

Frank and Michael

Announcement_10-fold_chapter_5

Chapter 3 released on YouTube

Chapter 3 is all about symmetry. We will start with the symmetries that can be found in everyday objects.

You will then learn how to classify crystals into their respective classes. We have prepared a small poster, so you can keep track of your very own collection of crystals.

Furthermore, we want to begin to talk about translational symmetry. This symmetry is a particular feature of crystal structures with their repetitive patterns.