Jinshajiangite: structure, twinning and pseudosymmetry.

Area of Science:

• Mineralogy
• Crystallography
• Materials Science

Background:

• Jinshajiangite is a titanium silicate mineral with a complex structure.
• Previous structural models for jinshajiangite and related minerals were based on inaccurate crystallographic data.

Purpose of the Study:

• To accurately determine the crystal structure of jinshajiangite using advanced analytical techniques.
• To clarify the structural relationships between jinshajiangite, perraultite, surkhobite, and bobshannonite.
• To propose a revised structural model for bafertisite.

Main Methods:

• Single-crystal X-ray diffraction
• Transmission electron microscopy

Main Results:

• The crystal structure of jinshajiangite was determined to be triclinic (P\bar 1 symmetry), with specific lattice parameters (a = 8.7331(2) Å, b = 8.7366(2) Å, c = 11.0404(3) Å, α = 81.477(1)°, β = 110.184(1)°, γ = 104.384(1)°).
• The determined structure differs significantly from the previously proposed monoclinic cell, featuring a single type of titanium silicate and cation layer.
• No significant iron-manganese ordering was observed despite high manganese content.
• All perraultite-type minerals share the P\bar 1 structure of jinshajiangite, with previously proposed monoclinic space groups attributed to polysynthetic twinning.

Conclusions:

• The study establishes the correct triclinic crystal structure for jinshajiangite.
• This revised understanding impacts the classification and structural interpretation of perraultite-group minerals.
• The findings provide a new polytype structure model for bafertisite, resolving structural ambiguities.