Monoclinic System
There are three axes, each of different lengths. Two are at right angles to each other and the third is inclined. Based on a parallelogram inner structure.
Crystal shapes include:
Common Monoclinic Crystals:
Azurite
Chrysocolla
Diopside
Epidote
Gypsum
Hiddenite
Howlite
Kunzite
Lazulite
Moonstone
Muscovite (Mica)
Petalite
Serpentine
Spodumene
Staurolite
Vivianite