Crystallographic data are lacking for berthierite because its imperfect morphological development prevents optical goniometric study. These data, however, have been easily obtained by Weissenberg methods. An equi inclination study leads to the following results:

Centrosymmetrical symmetry: mmm = Vh
Crystal system: orthorhombic
Unit cell: 
absolute ratio 
a = 11.44 Å 0.810 
b = 14.12 1.000 
c = 3.76 0.2663 
Z = 4 formula weights per cell. 
Diffraction symbol: mmmPna-.
Space group: Pna (C2v9) or Pnam (Vh16). 
Centrosymmetrical symmetry: mmm = Vh
Crystal system: orthorhombic
Unit cell: 
absolute ratio 
a = 11.44 Å 0.810 
b = 14.12 1.000 
c = 3.76 0.2663 
Z = 4 formula weights per cell. 
Diffraction symbol: mmmPna-.
Space group: Pna (C2v9) or Pnam (Vh16). 

The general geometry allows for 58 possible structures, but a simple intensity relation eliminates all but one, and definitely fixes the space group as Pnam. All atoms are on reflection planes (4c) with different parameters. Although an intensity-parameter study has not yet been made, a structure has been suggested based upon a substituted sphalerite type framework.

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