Eudialyte

Eudialyte is a rare and complex cyclosilicate mineral, one of the ring silicates in the silicate mineral group. It is known for vivid, colorful crystals and its occurrence in alkaline igneous rocks. The mineral has attracted interest in mineral collections and studies of silicate structure because of its intricate composition and crystal chemistry.

Chemical composition and structure: The formula of eudialyte is highly variable, reflecting extensive elemental substitutions. Typical constituents include sodium, calcium, and zirconium, with silicon and oxygen forming the silicate framework, and often hydroxide and chloride as additional anions. The structure features interconnected silicate rings that accommodate a variety of metallic cations, producing a range of color and composition in natural samples.

Physical properties: Eudialyte crystals are commonly pink to red, but may appear yellow, orange, or brown. The mineral has a vitreous (glassy) luster and is transparent to translucent in well-formed crystals. Its Mohs hardness is around 5.5 to 6, and it has a relatively moderate specific gravity near 3.2 to 3.3. Crystals are typically prismatic or tabular and may occur in aggregates or as well-formed individual specimens.

Occurrence and associations: Eudialyte forms in silica-undersaturated, alkaline igneous environments, particularly in nepheline syenites and related peralkaline rocks. It is commonly associated with other cyclosilicates and alkali minerals such as nepheline, cancrinite, and aegirine, reflecting its magmatic origin and the late-stage crystallization of alkaline systems.

Etymology and use: The name derives from Greek eu- meaning well and dialytos meaning dissolvable, in reference to its relatively easy dissolution in acids. Eudialyte is a minor source of zirconium and rare earth elements, but it is not a major ore mineral.