Building Trigonal and Rhombohedral Crystals with Unit Cells

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay

Technically, the unit cells of hexagonal and rhombohedral crystals are 60-120 prisms. However, that representation would result in models lacking 3- or 6-fold symmetry. Since hexagonal and rhombohedral unit cells can have any of three equivalent orientations, the best approach is to build models of triangular prisms. After all, the unit cell is an abstraction, not a physically real box.

Trigonal Prism

Trigonal Pyramid

Trigonal Dipyramid

Ditrigonal Prism

Ditrigonal Pyramid

Ditrigonal Dipyramid

Trigonal Trapezohedron

Ditrigonal Scalenohedron

This is how Rene Hauy deduced that minerals were made up of fundamental units.


Rhombohedron Built With Trigonal Unit Cells

Trigonal Compound Forms

Return to Symmetry Index

Return to Professor Dutch's home page

Created 18 Sept. 1997, Last Update 10 June 2020

Not an official UW-Green Bay site