Portselanis

Portselanis is a rare silicate mineral described in recent mineralogical literature. It forms colorless to pale blue prismatic crystals with a vitreous luster. On the Mohs scale it ranges from 6 to 7, and its standard density is about 3.2 g/cm3. Crystallography places portselanis in the monoclinic system, and optical properties are biaxial with refractive indices around 1.62 to 1.66. The mineral exhibits cleavage along preferred planes and can show faint pleochroism in polarized light.

Occurrence and geology describe portselanis as originating in high-temperature contact metamorphic zones associated with granitic intrusions. It has been found primarily in the Portse Basin region, where it occurs in intimate association with quartz, feldspar, magnetite, and cordierite. Detrital grains identified in regional sediments suggest a broader distribution than the primary source.

Etymology and naming explain that the term portselanis derives from the Portse region and the suffix -lanis, chosen to reflect its glassy, shimmering appearance under reflected light. The name was proposed by the discovery team in recognition of the mineral’s distinctive optical character.

Synthesis and applications summarize that portselanis can be produced in the laboratory through hydrothermal synthesis at temperatures of roughly 800–900°C and pressures of 2–5 kbar, starting from aluminosilicate precursors. Its stable crystal framework and optical properties give potential for use as a gemstone substitute and as a host material for luminescent dopants. Given its rarity, practical mining remains limited, and research continues to clarify its phase relations and long-term stability.

See also: List of minerals; Silicate minerals; Hydrothermal synthesis.