octaëdrale

Octaëdrale is a term used to describe objects, forms, or structures that exhibit the geometry of an octahedron. In French, the standard adjective is octaèdral (or octaédral); octaëdrale is a variant spelling that may appear in translations or specific usages. In English-language contexts, the common term is octahedral, but octaëdrale may be encountered in discussions of French terminology or older literature.

In geometry, an octahedron has eight triangular faces, six vertices, and twelve edges. The regular octahedron is the dual of the cube and possesses full octahedral symmetry (Oh), with a rotational subgroup of order 24. It is one of the five Platonic solids. Its geometry underpins many natural and man-made forms, including crystal facets and molecular coordination environments.

In chemistry, octahedral coordination describes a central atom or ion surrounded by six ligands at the corners of an octahedron. This geometry is common for many transition metal complexes and influences properties such as ligand-field splitting, spin state, and color. Complexes with Oh symmetry often arise when six identical ligands bind to a metal center.

In crystallography and mineralogy, octahedral forms appear in crystals of the isometric system; some minerals exhibit octahedral facets or habits. Diamond is a notable example where octahedral crystals can be observed, alongside other common crystal forms.

Notes: octaëdrale is primarily a linguistic variant; in most English-language texts, octahedral remains the standard term.