Suzukiite – polymorphic to Bavsiite

Suzukiite

• Named in honor of Jun Suzuki, a professor of mineralogy and petrology, at the Hokkaido University, Sapporo (Japan).
• Suzukiite belongs to the inosilicates (chain silicates) and is polymorphic to Bavsiite, which is tetragonal.
• Formula: BaVSi₂O₇
• Space group: Cmcm (No. 63)
• Crystal system: orthorhombic
• Crystal class: mmm
• Lattice parameters: a = 5.3546(16), b = 15.249(5) Å, c = 7.094(2) Å, α = β = γ = 90°

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Picture: D. Nishio-Hamane – CC BY-NC-SA 2.0

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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).)

 

• BaO₁₀ polyhedra (not shown as polyhedra, Ba green)
• SiO₄ tetrahedra (yellow)
• VO₅ square pyramids (purple)
• Oxygen (red)

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

https://skfb.ly/6Q6GC

Reference:
Crystal Structure of Suzukiite from the Mogurazawa Mine, Gunma Prefecture, Japan,
M. Ito, S. Matsubara, K. Yokoyama, K. Momma, R. Miyawaki, I. Nakai, A. Kato
Journal of Mineralogical and Petrological Sciences 2014, 109, 222-227

DOI: 10.2465/jmps.140520

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Dioptase: emerald-green and visible cleavage planes

Dioptase

• The name dioptase comes from the Greek words “dia” (= through) and “optos” (= visible), alluding to the visible cleavage planes inside the often highly transparent or translucent crystals
• Formula: CuSiO₃ · H₂O
• Space group: R-3 (No. 148)
• Crystal system: trigonal
• Crystal class: -3
• Lattice parameters: a = b = 14.566 Å, c = 7.778 Å, α = β = 90°, γ = 120°

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Dioptase Tsumeb

Picture: Didier Descouens – CC BY-SA 3.0

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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).)

View along the c axis.

• six SiO₄ tetrahedra (orange) are corner-connected to build a ring, so the mineral belongs to the cyclo silicates
• the copper atoms (blue) are octahedrally coordinated by six oxygen atoms (red), four of them are oxygens involved in SiO₄ tetrahedra and they occupy the equatorial positions of the CuO₆ octahedra and two of them are oxygen atoms of water molecules, which occupy the axial positions of the CuO₆ octahedra
• the CuO₆ octahedra are edge-connected and build a continuous 3D net

#141

I4₁/amd

Example – CeSiO₄

The crystal structures of CeSiO₄ and Ca₂Ce₈(SiO₄)₆O₂

Skakle, J.M.S., Dickson, C.L., Glasser, F.P
Powder Diffraction (2000) 15, 234-238

 

CIF
https://www.dropbox.com/s/h2ybb008bvbhajo/icsd_92040.cif

 

CeO8 polyhedra (lime)
SiO4 tetrahedra (orange)

3D rotatable model of CeSiO₄