stenull

Stenull is a hypothetical mineral species described in speculative mineralogy to denote a fibrous silicate phase observed in certain metamorphic rocks. The name is derived from combining a prefix implying narrow fibers with a reference to a woolly habit.

Description and properties: Stenull is reported as pale gray to white, with a silky to pearly luster and a distinctly fibrous or acicular habit. Individual crystals are slender and elongated, often forming dense mats. Reported physical properties include Mohs hardness around 4–6 and a density near 2.8–3.2 g/cm3; refractive indices have not been reliably determined, and there is no consensus on the crystal system.

Occurrence and formation: Reported in limited field samples from high-grade metamorphic belts and metasomatic environments where silica-rich rocks interact with fluid phases. The fibers are interpreted to crystallize along planes of weakness during elevated temperature and pressure, producing acicular aggregates. Identification relies on X-ray diffraction and electron microscopy; the material can be mistaken for other fibrous silicates or asbestos-like phases until a definite diffraction pattern is obtained.

Status and significance: Stenull has not been formally recognized by the International Mineralogical Association, and its status remains provisional. In speculative literature, stenull is discussed as a potential marker mineral for certain metamorphic conditions and as a model for studying fibrous mineral growth. No practical industrial applications have been demonstrated, and synthetic production has not been reported.