Monoclinic crystal system

A crystal system with three unequal unit-cell axes, two oblique angles, and one right angle. Its symmetry is lower than orthorhombic and higher than triclinic.

Unit cell: The smallest repeating structural unit whose translations generate a crystal lattice. Its three edge lengths and angles supply the geometric parameters used to classify monoclinic crystals.
Monoclinic lattice: A lattice whose conventional unit cell has unequal edge lengths, one oblique angle, and two right angles. It is the lattice geometry underlying the monoclinic crystal system.
Triclinic crystal system: A crystal system with three unequal unit-cell axes and three non-right angles. It allows fewer geometric constraints than the monoclinic system.
Gypsum: A hydrated calcium sulfate mineral that commonly forms tabular or fibrous crystals. Gypsum is a familiar mineral that crystallizes in the monoclinic system.
Crystal system: A classification of crystal lattices by their unit-cell geometry and symmetry. Monoclinic is one of the seven systems in this classification.
Unique axis: A crystallographic axis distinguished by the symmetry operations or conventional setting of a crystal. In the standard monoclinic setting, the unique axis is commonly the b axis.
Orthorhombic crystal system: A crystal system with three unequal unit-cell axes and three right angles. Changing the monoclinic oblique angle to 90 degrees yields orthorhombic geometry.
Orthoclase: A potassium-rich feldspar mineral with a monoclinic crystal structure. Its structure provides a well-known monoclinic example among rock-forming minerals.
Lattice system: A grouping of Bravais lattices according to their lattice metric and symmetry. It relates the monoclinic geometry to the lattice types compatible with it.
Monoclinic symmetry: Crystal symmetry containing at most one twofold axis or one mirror plane as its principal nontrivial operation. This limited symmetry permits only one conventional cell angle to depart from 90 degrees.

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