Triklinen

Triklinen, in crystallography often rendered as triclinic in English, denotes one of the seven crystal systems. It is the least symmetric and most general system, encompassing crystals whose internal lattice lacks any axis of equal length or right angle between axes.

The triclinic unit cell is defined by three unequal edge lengths a, b, and c, with all interaxial angles α, β, and γ also different from each other and from 90 degrees. In other words, no angle is constrained to be 90°, and the axes are oblique. This general geometry means triclinic crystals can assume a wide range of shapes, from elongated prisms to more irregular forms.

In terms of symmetry, the triclinic system has the lowest possible crystal symmetry. The point groups compatible with triclinic lattices are 1 and -1, corresponding to crystals with no symmetry or with an inversion center. The space groups associated with the triclinic system are P1 and P-1, the two simplest space groups in crystallography.

Most minerals that crystallize in the triclinic system are characterized by minimal symmetry, which often leads to complex external forms and variable cleavage. Common examples include many plagioclase feldspars and microcline, a potassium feldspar, both associated with triclinic arrangements.

Overall, triklinen crystals are defined by their oblique, non-orthogonal lattice and lack of higher symmetry, making them the most general and unconstrained of the crystal systems.