Vermiculite – Mineral of the Year 2019 in Austria

Vermiculite

• The mineral was first described in 1824 by Thomas H. Webb. Due to the property of the mineral to expand into worm-like formations when heated to 200 to 300 °C in the direction of the crystallographic c-axis, Webb named it after the Latin word “vermiculor” for “worm breeder”.
• On the occasion of the 195th anniversary of its discovery and due to its great importance as an industrial mineral, vermiculite was voted “Mineral of the Year” in Austria in 2019.
• Formula: Mg_0,7(Mg,Fe,Al)₆(Si,Al)₈O₂₀(OH)₄ · 8 H₂O
• Space group: C2/c (No. 15)
• Crystal system: monoclinic
• Crystal class: 2/m
• Lattice parameters: a = 5.349 Å, b = 9.255 Å, c = 28.89, α = γ = 90°, β = 97.12°

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Picture: CC BY-SA 3.0 Leon Hupperichs

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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).)

• Mg: green, Si: yellow, Al: blueish, O: red
• MgO₆ octahedra (green), Si/AlO₄ tetrahedra (yellow)
• Reference: Crystal structure of a two-layer Mg-vermiculite
  H. Shirozu, S.W. Bailey
  American Mineralogist (1966) 51 (7): 1124-1143.
  http://www.minsocam.org/msa/collectors_corner/amtoc/toc1966.htm

For a 3D interactive version on sketchfab, see here:

https://skfb.ly/6OKvO

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