Haavandite

Haavandite is a rare silicate mineral described from metamorphic and hydrothermal environments. It is considered part of the silicate group and is typically associated with low- to mid-temperature metamorphic rocks, often found in schist, greisen, and quartz-vein zones. The mineral was named for its type locality in the Haavand region, reflecting common practice in mineral nomenclature.

Occurrence and locality: Haavandite has been reported primarily in the Haavand area of Norway, with additional specimens found in alpine-type metamorphic belts elsewhere. It forms in veins and pockets where fluids supply calcium, aluminum, silicon, and alkali metals. Associated minerals commonly include quartz, muscovite, calcite, and minor rutile or hematite.

Chemical composition and structure: Analyses indicate haavandite is rich in calcium, silicon, aluminum, and alkali metals such as sodium and potassium, with trace amounts of iron and titanium. The ideal formula is not universally agreed, and the mineral is described as a hydrous silicate with variable alkali content. Structurally, it is interpreted as a sheet- or framework-type silicate with hydroxyl groups integrated into the lattice.

Physical properties: Haavandite typically appears as pale green to yellow-brown prismatic to tabular crystals, with a vitreous to adamantine luster. It is translucent to opaque, has a Mohs hardness around 5–6, and a specific gravity near 3.1–3.5. Cleavage is imperfect, and optical properties are commonly reported as biaxial with moderate refractive indices.

Discovery and naming: The name haavandite derives from the type locality. Initial descriptions and subsequent analyses were published by regional mineral researchers in the 1990s and early 2000s, contributing to its recognition as a distinct mineral species.

References: Descriptions appear in regional mineral catalogs and journals detailing newly described silicates and their characteristic properties.