Rebendite

Rebendite is a hypothetical mineral species used in geology education to illustrate mineral classification and nomenclature. It is not currently recognized as a real mineral by major reference works such as Mindat or the Handbook of Mineralogy. The name rebendite is a coinage used in problem sets and textbooks to discuss how minerals are defined and described.

Composition and structure: In educational models, rebendite is described as a silicate mineral with a general formula M2Si2O7 (hypothetical), where M represents alkali or alkaline-earth metals. It is posited to crystallize in the monoclinic system, forming prismatic crystals.

Physical properties: In teaching contexts, rebendite is described as colorless to pale green, with a vitreous luster, and a Mohs hardness of 5.5–6.0. It is imagined to have two good cleavages and to be transparent to translucent. Specific gravity is typically placed around 2.9–3.2.

Occurrence and formation: In educational scenarios, rebendite is said to form during late-stage crystallization of granitic rocks or in pegmatites, typically in association with quartz, plagioclase, and muscovite in textbook illustrations. The mineral is used to demonstrate isomorphic substitutions and the effect of composition on optical properties.

Uses and significance: The mineral serves as a stand-in for discussions of mineral nomenclature, crystallography, and X-ray diffraction patterns. It provides a consistent example for defining terms such as streak, fracture, cleavage, and habit, helping students understand how real minerals are described and categorized.