The Seven Crystal Systems
The seven crystal systems are a method of classifying crystals according
to their atomic lattice or structure. The atomic lattice is a three dimensional
network of atoms that are arranged in a symmetrical pattern. The shape of the
lattice determines not only which crystal system the stone belongs to, but all
of its physical properties and appearance. In some crystal healing practices
the axial symmetry of a crystal is believed to directly influence its
metaphysical properties. For example crystals in the Cubic System are believed to
be grounding, because the cube is a symbol of the element Earth.
There are seven crystal systems or
groups, each of which has a distinct atomic lattice. Here we have outlined the
basic atomic structure of the seven systems, along with some common examples of
each system.
Cubic System
Also known as the isometric system.
All three axes are of equal length and intersect at right angles. Based on a square inner structure.
Crystal shapes include:
- Cube (diamond, fluorite, pyrite)
- Octahedron (diamond, fluorite, magnetite)
- Rhombic dodecahedron (garnet, lapis
lazuli rarely crystallises)
- Icosi-tetrahedron (pyrite, sphalerite)
- Hexacisochedron (pyrite).
Common Cubic Crystals:
|
Diamond |
Fluorite |
Garnet |
|
Gold |
Pyrite |
Silver |
|
Spinel |
||
Tetragonal System
Two axes are of equal length and are
in the same plane, the main axis is either longer or shorter, and all three
intersect at right angles.
Based on a rectangular inner structure.
Crystal shapes include:
- Four-sided prisms and pyramids
- Trapezohedrons
- Eight-sided and double pyramids
- Icosi-tetrahedron (pyrite, sphalerite)
- Hexacisochedron (pyrite).
Common Tetragonal Crystals:
|
Anatase |
Apophyllite |
Chalcopyrite |
|
Rutile |
Scapolite |
Scheelite |
|
Wulfenite |
Zircon |
Hexagonal System
Three out of the four axes are in
one plane, of the same length, and intersect each other at angles of 60
degrees. The fourth axis is of a different length and intersects the others at
right angles.
Based on a hexagonal (6-sided) inner structure.
Crystal shapes include:
- Four-sided prisms and pyramids
- Twelve-sided pyramids
- Double pyramids
Common Hexagonal Crystals:
|
Apatite |
Aquamarine |
Beryl |
|
Cancrinite |
Emerald |
Goshenite |
|
Morganite |
Sugilite |
Zincite |
Trigonal System
(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.
Crystal shapes include:
- Three-sided prisms or pyramids
- Rhombohedra
- Scalenohedra
Common Trigonal Crystals:
|
Agate |
Amethyst |
Aventurine |
|
Calcite |
Carnelian |
Citrine |
|
Hematite |
Jasper |
Phenakite |
|
Quartz |
Rhodochrosite |
Rose
Quartz (rarely crystallises) |
|
Ruby |
Sapphire |
Smoky
Quartz |
|
Tigers
Eye |
Tourmaline |
|
Orthorhombic System
(Rhombic System)Three axes, all of
different lengths, are at right angles to each other.
Based on a rhombic (diamond-shaped) inner structure.
Crystal shapes include:
- Pinacoids
- Rhombic prisms
- Pyramids
- Double pyramids
Common Orthorhombic Crystals:
|
Alexandrite |
Andalusite (Chiastolite) |
Celestite |
|
Chrysoberyl |
Chrysoberyl |
Danburite |
|
Dumortierite |
Enstatite |
Hemimorphite |
|
Iolite |
Tanzanite |
Topaz |
|
Zoisite |
||
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:
- Basal pinacoids and
prisms with inclined end faces
Common Monoclinic Crystals:
|
Azurite |
Chrysocolla |
Diopside |
|
Epidote |
Gypsum |
Hiddenite |
|
Howlite |
Kunzite |
Lazulite |
|
Moonstone |
Muscovite
(Mica) |
Petalite |
|
Serpentine |
Spodumene |
Staurolite |
|
Vivianite |
||
Triclinic System
All three axes are of different
lengths and inclined towards each other.
Based on a 'triclinic' inner structure, meaning 'three inclined angles'.
Crystal forms are usually paired
faces.
Common Triclinic Crystals:
|
Amazonite |
Aventurine Feldspar |
Kyanite |
|
Labradorite |
Rhodonite |
Turquoise |
Amorphous
No crystal structure. Most of these
are either cooled too quickly to crystallise - such as obsidian or moldavite, or are organic - such as amber.
Common Amorphous Minerals:
|
Amber |
Moldavite |
Obsidian |
|
Opal |