Rhombohedrakiteitä

Rhombohedrakiteitä is a Finnish mineralogical term used to describe minerals that crystallize in the rhombohedral geometry and typically form rhombohedral crystals. The term emphasizes the rhombohedral morphology associated with the rhombohedral subset of the trigonal crystal system. In practice, rhombohedrakiteitä are identified by their characteristic rhombohedral crystal faces and, in many specimens, rhombohedral cleavage. The expression is mainly used in educational and descriptive contexts; in international mineralogy these minerals are more commonly discussed in terms of their crystal system and mineral species.

Occurrence and formation: Rhombohedrakiteitä occur in a range of geological settings, notably in sedimentary carbonate rocks such as limestone and dolostone, as well as in hydrothermal and metamorphic environments where rhombohedral carbonates crystallize. Growth conditions that favor rhombohedron formation influence both habit and cleavage.

Examples: Classic rhombohedral carbonates, such as calcite and dolomite, are typical members of this habit. Other minerals can exhibit rhombohedral morphologies under certain environmental conditions, including some nitrates and borates.

Properties: Physical properties vary by species but commonly include a relatively low hardness (calcite around 3 on the Mohs scale) and a distinctive rhombohedral cleavage. Luster is often vitreous to resinous, with optical properties that reflect the underlying rhombohedral symmetry.

Relation to terminology: The phrase rhombohedrakiteitä does not denote a single universally defined mineral species; rather, it describes a descriptive category used in some Finnish texts to refer to rhombohedral minerals with rhombohedral crystal habits. See also rhombohedral crystal system, calcite, dolomite.