Open Adit™ - The Hexagonal System

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Of the four axes in hexagonal crystals, three in one plane are equal in length and meet at 120° angles, while the fourth (which is either shorter or longer) meets the others at 90°. Although these axes also characterize the triagonal system, the two systems differ in other ways, such as in the elements of symmetry. the six sided crystals may be hexagons, plates or pyramids.

The hexagonal crystal system is divided into the hexagonal and rhombohedral or triagonal divisions. All crystals of the hexagonal division possess a single 6-fold axis of rotation. In addition to the single 6-fold axis of rotation, crystals of the hexagonal division may possess up to six 2-fold axes of rotation. They may demonstrate a center of inversion symmetry and up to seven mirror planes. Crystals of the triagonal division all possess a single 3-fold axis of rotation rather than the 6-fold axis of the hexagonal division. Crystals of this division may possess up to three 2-fold axes of rotation and may demonstrate a center of inversion and up to three mirror planes.

In the hexagonal system are found nearly 8% of all minerals, including apatite, graphite, ice, beryl, and molybdenite.


12 crystal classes divided into 2 groups Hexagonal division with a 6-fold symmetry axis Rhombohedral division have a 3-fold symmetry axis Four crystallographic axes of equal length with angels of 120 degrees. The fourth axis is vertical.

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