(Rhombohedral System) - Axes and angles in this system are similar to the Hexagonal System, and the two systems are often combined as Hexagonal. In the cross-section of a Hexagonal crystal, there will be six sides. In the cross-section of a Trigonal crystal there will be three sides.
Based on a triangular inner structure.
- Three-sided prisms or pyramids
Some Trigonal Crystals:
- Rose Quartz
- Ruby, Sapphire
- Smoky Quartz
- Tigers Eye