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There are six, some say seven, basic crystal classes of minerals. The fundamental symmetry properties are listed below. The classes are subdivided into crystal forms. Underlying pages have paper models of these forms.
Crystal Classes and Forms: Models
Hexagonal
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Trigonal
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Monoclinic
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Triclinic
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Crystal Classes: Simple to Complex Symmetry from bottom to top
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Isometric |
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m3m |
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43m |
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432 |
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m3 |
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6/mmm |
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Hexagonal |
Tetragonal |
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4/mmm |
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23 |
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6mm |
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6m2 |
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622 |
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6/m |
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3m |
42m |
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4mm |
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422 |
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4/m |
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mmm |
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3m |
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32 |
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3 |
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6 |
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6 |
4 |
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mm2 |
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222 |
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4 |
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2/m |
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Monoclinic |
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Orthorhombic |
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3 |
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Trigonal |
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m |
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2 |
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1 |
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1 |
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Triclinic |
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Crystal Classes and Basis Forms: Simple to Complex Symmetry from top to bottom
Triclinic |
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Basis Model |
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Class |
Axes |
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Planes |
Center |
Symmetry |
Hermann-Maugin |
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2-Fold |
3-Fold |
4-Fold |
6-Fold |
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Pedial |
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none |
1 |
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Pinacoidal |
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yes |
i |
1 |
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Monoclinic |
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Basis Model |
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Class |
Axes |
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Planes |
Center |
Symmetry |
Hermann-Maugin |
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2-Fold |
3-Fold |
4-Fold |
6-Fold |
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Sphenoidal |
1 |
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1A2 |
2 |
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Domatic |
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1 |
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1m |
m |
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Prismatic |
1 |
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1 |
yes |
i, 1A2, 1m |
2/m |
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Orthorhombic |
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Basis Model |
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Class |
Axes |
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Planes |
Center |
Symmetry |
Hermann-Maugin |
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2-Fold |
3-Fold |
4-Fold |
6-Fold |
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Rhombic-Pyramidal |
1 |
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2 |
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1A2, 2m |
mm2
(2mm) |
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Rhombic-Disphenoidal |
3 |
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3A2 |
222 |
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Rhombic-Dipyramidal |
3 |
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3 |
yes |
i, 3A2, 3m |
2/m2/m2/m
(mmm) |
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Trigonal |
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Basis Model |
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Class |
Axes |
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Planes |
Center |
Symmetry |
Hermann-Maugin |
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2-Fold |
3-Fold |
4-Fold |
6-Fold |
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Trigonal-Pyramidal |
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1 |
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1A3 |
3 |
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Ditrigonal-Pyramidal |
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1 |
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3 |
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1A3, 3m |
3m |
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Rhombohedral |
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1 |
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yes |
1A3 |
3 |
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Trigonal-Trapezohedral |
3 |
1 |
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1A3, 3A2 |
32 |
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Hexagonal-Scalenohedral |
3 |
1 |
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3 |
yes |
1A3, 3A2, 3m |
32/m
(3m) |
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Tetragonal |
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Basis Model |
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Class |
Axes |
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Planes |
Center |
Symmetry |
Hermann-Maugin |
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2-Fold |
3-Fold |
4-Fold |
6-Fold |
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Tetragonal-Disphenoidal |
1 |
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A4 |
4 |
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Tetragonal-Pyramidal |
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1 |
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1A4 |
4 |
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Tetragonal-Dipyramidal |
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1 |
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1 |
yes |
i, 1A4, 1m |
4/m |
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Ditetragonal-Pyramidal |
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4 |
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1A4, 4m |
4mm |
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Ditetragonal-Dipyramidal |
4 |
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1 |
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5 |
yes |
i, 1A4, 4A2, 5m |
4/mmm
(4/m2/m2/m) |
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Tetragonal-Scalenohedral |
3 |
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2 |
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1A4, 2A2, 2m |
42m |
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Tetragonal-Trapezohedral |
4 |
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1 |
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1A4, 2A2 |
422 |
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Hexagonal |
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Basis Model |
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Class |
Axes |
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Planes |
Center |
Symmetry |
Hermann-Maugin |
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2-Fold |
3-Fold |
4-Fold |
6-Fold |
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Hexagonal-Pyramidal |
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1 |
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1A6 |
6 |
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Hexagonal-Dipyramidal |
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1 |
1 |
yes |
i, 1A6, 1m |
6/m |
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Trigonal-Dipyramidal |
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1 |
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1 |
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1A6 |
6 |
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Dihexagonal-Pyramidal |
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1 |
6 |
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1A6, 6m |
6mm |
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Ditrigonal-Dipyramidal |
3 |
1 |
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4 |
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1A6, 3A2, 3m |
6m2 |
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Hexagonal-Trapezohedral |
6 |
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1 |
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1A6, 6A2 |
622 |
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Dihexagonal-Dipyramidal |
6 |
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1 |
7 |
yes |
i, 1A6, 6A2, 7m |
6/m2/m2/m
(6/mmm) |
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Isometric |
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Basis Model |
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Class |
Axes |
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Planes |
Center |
Symmetry |
Hermann-Maugin |
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2-Fold |
3-Fold |
4-Fold |
6-Fold |
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Tetaroidal |
3 |
4 |
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3A2, 4A3 |
23 |
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Diploidal |
3 |
4 |
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3 |
yes |
3A2, 3m, 4A3 |
2/m3
(m3) |
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