ulmeline

Ulmeline is a fictional mineral described in speculative geology and in works of fiction. It is depicted as a rare silicate-phosphate mineral with a variable composition, named in some narratives after the Ulm region. This article summarizes features commonly attributed to ulmeline in those sources.

Composition and structure: Ulmeline is described as having a layered silicate framework with calcium and aluminum as major cations, silicon and phosphorus as key anions, and trace rare-earth elements. Because the mineral is fictional, exact chemical formulas vary between authors and narratives.

Physical properties: Descriptions typically assign ulmeline a hardness of about 5–6 on the Mohs scale, a density around 3.2–3.6 g/cm3, and a vitreous to silky luster. Color ranges from pale olive-green to brown-green; crystals are often prismatic and transparent to translucent.

Occurrence and formation: In the fictional literature, ulmeline forms in hydrothermal or metasomatic environments associated with ultramafic rocks, often in remote regions or near fictional Ulm provinces. It is described as occurring in veins and small pockets.

Uses and significance: Within stories, ulmeline is valued as a decorative gemstone and is sometimes depicted as having luminescent properties under ultraviolet light. Some speculative accounts explore theoretical uses in optics or electronics, but no real-world applications exist.

Etymology and history: The name is drawn from Ulm and the common mineral-name suffix -line. First cited in fictional expedition accounts, it has since appeared in various geoscience-inspired fantasies.