Crystal Systems: The 7 Ways Minerals Crystallize

All minerals crystallize in one of seven crystal systems based on their symmetry. Cubic (isometric) has three equal axes at 90 degrees. Tetragonal has two equal axes and one different, all at 90.

Orthorhombic has three unequal axes at 90. Hexagonal has three equal axes at 120 plus one perpendicular. Trigonal is a subdivision of hexagonal.

Monoclinic has three unequal axes, two at 90, one not. Triclinic has three unequal axes, none at 90. The crystal system reflects the internal atomic arrangement..