The study of crystals is called Crystallography.
All minerals have a regular crystal structure. This structure is made up of many flat surfaces which are called faces. When these crystal faces join together they form a crystal. The structure a group of crystal faces form is called a crystal system. Although there are over
3,500 different minerals that have been identified, they all fall into one of seven crystal systems.
The seven crystal systems are:
- The Cubic System
(also called the Isometric System)
includes the minerals diamond, galena, gold, silver, fluorite, garnet, halite and copper.
- The Hexagonal System includes the minerals emerald, benitoite, graphite, molybdenite, and vanadinite.
- The Rhombohedral System includes the minerals calcite, quartz, rhodochrosite, siderite and dolomite. This is a branch of the hexagonal system.
- The Tetragonal System includes the minerals rutile, scapolite, wulfenite and zircon.
- The Orthorhombic System includes the minerals aragonite, barite, celestite, goethite, and marcasite.
The Monoclinic System includes the minerals gypsum, augite, biotite, epidote, and hornblende.
The Triclinic System includes the minerals plagioclase feldspar, ulexite, turquoise, and albite.