Mineralogy Database

Crystallography

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Crystallography and Minerals Arranged by Crystal Form

Amorphous Isometric Tetragonal Orthorhombic Hexagonal Trigonal Monoclinic Triclinic
Amorphous Minerals Isometric (Cubic) Minerals Tetragonal Minerals Orthorhombic Minerals Hexagonal Minerals Trigonal Minerals Monoclinic Minerals Triclinic Minerals

Crystal Groups and Classes - Crystallography groups are composed of 32 classes of symmetry derived from observations of the external crystal form.  From these 32 classes, 230 space groups (see Crystallography 101) are distinguishable using x-ray analysis.  For additional information on crystal systems, please review an excellent on-line treatment of this subject, the Introduction to Crystallography and Mineral Crystal Systems by Mike and Darcy Howard.

Example Crystal Morphology - To further illustrate these symmetry elements, the example crystalline forms for each symmetry class were constructed using Faces (version 3.7) by Georges Favreau for older browsers and a JAVA language program called JCrystal by Steffen Weber for the java-capable browsers. In addition, Steffen Weber has a new version of JCrystal called KrystalShaper that can produce paper models of the example crystals.    The paper models for each crystal class have been reproduced in .pdf format (see below) and can be printed on heavy card stock to construct a physical model. Please note: the paper model forms may be simplified from the JCrystal forms to avoid overly-complicated cutting.

The example crystals in each group and class were constructed using the following parameters:

  • Crystallographic axes: a=1, b=1, c=1.
  • Forms: [214], [104], [024], [100], [010] (Color coded in all example crystals).

This morphology was used in all the crystal groups and classes for drawing the examples and the stereo images. The higher order forms were selected to best illustrate some of the subtle differences in the symmetry classes. Remember, most real crystals will probably not have similar forms when compared to the examples.

Table Crystallography (Mason 68, p18) - The thirty-two crystal classes are summarized by symmetry elements in the following table which is linked to:

  1. Example crystal images within the crystallography group in the yellow columns.
  2. Stereo crystal images/java example and mineral listings of each group and class in the green columns.
  3. JAVA crystal examples on the individual crystal classes for detailed study. Please note that the rotational inversion axes of 3,(3BAR) 4 (4BAR), and 6 (6BAR) may not be visible to older browsers which don't use cascading style sheets (.css).
System (1) Class Name (2)

AXES

Planes Center
Hermann-
Maugin
Symbols (3)
2-Fold 3-Fold 4-Fold 6-Fold
Isometric

 

 

Tetartoidal 3 4 - - - - 23
Diploidal 3 4 - - 3 yes 2/m 3
Hextetrahedral 3 4 - - 6 - 4 3m
Gyroidal 6 4 3 - - - 432
Hexoctahedral 6 4 3 - 9 yes 4/m 3 2/m
Tetragonal

 

 

 

Disphenoidal 1 - - - - - 4
Pyramidal - - 1 - - - 4
Dipyramidal - - 1 - 1 yes 4/m
3 - - - 2 - 4 2m
Ditetragonal pyramidal - - - - 4 - 4mm
Trapezohedral 4 - 1 - - - 422
Ditetragonal-Dipyramidal 4 - 1 - 5 yes 4/m 2/m 2/m
Orthorhombic

 

Pyramidal 1 - - - 2 - mm2
Disphenoidal 3 - - - - - 222
Dipyramidal 3 - - - 3 yes 2/m 2/m 2/m
Hexagonal

 

 

 

Trigonal Dipyramidal - 1 - - 1 - 6
Pyramidal - - - 1 - - 6
Dipyramidal - - - 1 1 yes 6/m
Ditrigonal Dipyramidal 3 1 - - 4 - 6m2
Dihexagonal Pyramidal - - - 1 6 - 6mm
Trapezohedral 6 - - 1 - - 622
Dihexagonal Dipyramidal 6 - - 1 7 yes 6/m 2/m 2/m
Trigonal

 

 

Pyramidal - 1 - - - - 3
Rhombohedral - 1 - - - yes 3
Ditrigonal Pyramidal - 1 - - 3 - 3m
Trapezohedral 3 1 - - - - 32
Hexagonal Scalenohedral 3 1 - - 3 yes 3 2/m
Monoclinic

 

Domatic - - - - 1 - m
Sphenoidal 1 - - - - - 2
Prismatic 1 - - - 1 yes 2/m
Triclinic Pedial - - - - - - 1
Pinacoidal - - - - - yes 1

Isometric System - Axial Diagram, Paper Model and KrystalShaper Form
Tetragonal System - Axial Diagram, Paper Model and KrystalShaper Form
Orthorhombic System - Axial Diagram, Paper Model and KrystalShaper Form
Hexagonal System - Axial Diagram, Paper Model and KrystalShaper Form
Trigonal System - Axial Diagram, Paper Model and KrystalShaper Form
Monoclinic System - Axial Diagram, Paper Model and KrystalShaper Form
Triclinic System - Axial Diagram, Paper Model and KrystalShaper Form