Erdradien

Erdradien is a rare silicate mineral that forms in metamorphic and hydrothermal settings. It is distinguished by a layered crystal structure and a pale olive-green to emerald color in transmitted light. In hand specimen it commonly exhibits a vitreous to resinous luster and a light streak.

Etymology and discovery

The name Erdradien derives from the fictional Erdradia region, where the mineral was first described by mineralogist L. Kaza in 2002. The term reflects a combination of the regional toponym and the standard mineral suffix used in mineral nomenclature.

Composition and structure

Chemically, Erdradien shows a solid solution between aluminum-rich phyllosilicate phases with minor iron and trace rare-earth elements; the exact formula varies with sample. It crystallizes in the monoclinic system, typically as short prismatic to tabular crystals that may be twinned or intergrown. Physical-property estimates include refractive indices around nα ≈ 1.60–1.62, nβ ≈ 1.63–1.66, and nγ ≈ 1.66–1.68, with modest birefringence. Specific gravity ranges from about 3.0 to 3.4. Cleavage is typically imperfect in one plane with varying basal tendencies.

Occurrence and geology

Erdradien occurs in low-grade metamorphic zones within ultramafic rocks and in hydrothermal veins, often alongside serpentine, olivine, pyroxene, and magnetite. It is commonly found with chlorite and calcite in vein-rich metamorphic environments, where fluid activity promotes its formation and growth.

Uses and significance

Due to its rarity and variable clarity, Erdradien is not widely used as a gemstone. When polished, gem-quality material is highly valued by collectors and researchers. The mineral is of interest for studies of metamorphic processes and solid-solution behavior in silicate systems, rather than for bulk industrial applications.