Monthly Archives: October 2016

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)

Selected Minerals – Today: Aragonite

Aragonite

  • Named after the type locality Aragon (Spain)
  • One of the two naturally occuring forms of calcium carbonate (the other being calcite)
  • Formula: CaCO3
  • Space group: Pmcn (No. 62)
  • Crystal system: orthorhombic
  • Crystal class: mmm
  • Lattice parameters: a = 4.95 Å, b = 7.96 Å, c = 5.74, αβγ = 90°

aragonite-196792

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


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

aragonite

CO3 triangles (black), CaO9 irregular polyhedra (blue)

Selected Minerals – Today: Anglesite

Anglesite

  • Named after the type locality (a locality, where a a particuliar mineral was first found/identified), which is here the Isle of Anglesey (Wales)
  • Occurs as an oxidation product of primary lead sulfide (PbS, Galena) ore
  • Formula: PbSO4
  • Space group: Pnma (No. 62)
  • Crystal system: orthorhombic
  • Crystal class: mmm
  • Lattice parameters: a = 8.48 Å, b = 5.40 Å, c = 6.96, αβγ = 90°

anglesite-anglesitetoussitminemorocco

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


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

pbso4_anglesite

SO4 tetrahedra (yellow), PbO8 irregular polyhedra (gray)

Selected Minerals – Today: Adamite

Adamite

  • Named after the French mineralogist Gilbert-Joseph Adam (1795 – 1881)
  • Typically occuring in weathered zones above zink ores
  • Formula: Zn2(OH)(AsO4)
  • Space group: Pnnm (No. 58)
  • Crystal system: orthorhombic
  • Crystal class: mmm
  • Lattice parameters: a = 8.30 Å, b = 8.51 Å, c = 6.04, αβγ = 90°

adamite-139150

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


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

adamite

AsO4 tetrahedra (green), ZnO6 octahedra (gray)