# Seven crystal systems

The terms crystal system, crystal family, and lattice system each refer to one of several classes of space groups, lattices, point groups, or crystals. Informally, two crystals are in the same crystal system if they have similar symmetries, though there are many exceptions to this.

The volume of the unit cell can be calculated from the lattice constant lengths and angles. If the unit cell sides are represented as vectors, then the volume is the dot product of one vector with the cross product of the other two vectors. The volume is represented by the letter V. 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. Seven distinct unit cells can be recognised for 3-D lattices. The seven unit cells are associated with seven systems of crystal axes called the seven crystal systems.The structures of all crystals can be classified according to the symmetry of the unit cells. There are in total 7 groups, collectively called Crystal Systems: Tricinic, Monoclinic, Orthorhombic, Tetragonal, Trigonal, Hexagonal, and Cubic.

There are seven crystal systems or groups, each of which has a distinct atomic lattice.

#### Cubic System

All three axes are equal of length and intersect at rigth angle.

#### 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.

#### 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.

#### Trigonal 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.

#### Orthorhombic System

Three axes, all of different lengths, are at right angles to each other.

#### 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.

#### Triclinic System

All three axes are of different lengths and inclined towards each other.Based on a 'triclinic' inner structure, meaning 'three inclined angles

#### 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.