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 Systemcubic crystal 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:

Common Cubic Crystals:

Diamond

Fluorite

Garnet

Gold

Pyrite

Silver

Spinel

Tetragonal SystemTetragonal crystal 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:

Common Tetragonal Crystals:

Anatase

Apophyllite

Chalcopyrite

Rutile

Scapolite

Scheelite

Wulfenite

Zircon

Hexagonal Systemhexagonal crystal 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:

Common Hexagonal Crystals:

Apatite

Aquamarine

Beryl

Cancrinite

Emerald

Goshenite

Morganite

Sugilite

Zincite

Trigonal Systemtrigonal crystal 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:

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 Systemorthorhombic crystal 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:

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:

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