From The Gemology Project
Crystal Systems & Forms
Crystal System

Diagram

Examples

Cubic
The cube is composed of 6 square faces
at 90 degree angles to each other. Each
face intersects one of the crystallographic
axes and is parallel to the other two.


Diamond
Garnet
Spinel

Tetragonal
The tetragonal system also has three axes
that all meet at 90°. It differs from the
isometric system in that the C axis is longer
than the A and B axis which are the same length
that all meet at 90°. It differs from the isometric
system in that the C axis is longer than the A
and B axis which are the same length.


Zircon

Hexagonal
In the hexagonal system we have an additional axes,
which gives the crystals six sides. Three of these
are equal in length and meet at 60° to each other.
The C or vertical axis is at 90° to the shorter axes.
Mineralogists sometimes divide this into two systems,
the hexagonal and the trigonal, based on their external
appearance, as follows:


Aquamarine
Benitoite
Beryl
Citrine
Emerald
Heliodor
Morganite
Quartz
Ruby
Sapphire
