Triclinic crystal system

An article about the triclinic crystal system in crystallography

Overview

The triclinic crystal system is one of the seven crystal systems in crystallography. It is the least symmetric of all the crystal systems, characterized by three axes of unequal length that intersect at oblique angles. This system is defined by the absence of any symmetry other than the identity operation.

Characteristics

In the triclinic system, the unit cell is defined by three vectors of unequal length, denoted as \(a\), \(b\), and \(c\). The angles between these vectors, \(\alpha\), \(\beta\), and \(\gamma\), are all different and none of them are 90 degrees. This lack of symmetry results in a very flexible and adaptable structure, allowing for a wide variety of crystal shapes.

Crystallographic Axes

Microcline, a mineral that crystallizes in the triclinic system

The axes in the triclinic system are labeled as \(a\), \(b\), and \(c\), with the angles \(\alpha\), \(\beta\), and \(\gamma\) representing the angles between \(b\) and \(c\), \(a\) and \(c\), and \(a\) and \(b\) respectively. The general conditions for the triclinic system are:

• \(a \neq b \neq c\)
• \(\alpha \neq \beta \neq \gamma \neq 90^\circ\)

Examples

One of the most well-known minerals that crystallizes in the triclinic system is microcline, a type of feldspar. Microcline is often found in granite and is known for its distinctive grid-like twinning pattern, known as "tartan twinning".

Symmetry

The triclinic system has the lowest symmetry of all the crystal systems. It possesses only a single symmetry operation, which is the identity operation. This means that there are no rotational or reflectional symmetries present in the triclinic system.

Related pages

• Crystal system
• Crystallography
• Microcline
• Feldspar