leucothites

Leucothites are a mineral species described in mineralogical literature as pale, white to colorless silicate minerals that belong to the feldspathoid-related group. The name combines the Greek elements leukos, white, and lithos, stone, reflecting their characteristic light appearance.

Description and properties

Leucothites typically occur as short prismatic to tabular crystals or as fine-grained to compact masses. They exhibit a vitreous to pearly luster and a pale to colorless body color. Crystal systems reported for leucothites include monoclinic, with imperfect cleavage and a conchoidal to uneven fracture. Hardness is generally in the mid-range (approximately 5 to 6 on the Mohs scale), and measured densities fall near 2.9 to 3.2 g/cm3. The mineral displays varying optical properties, with low to moderate relief and refractive indices that correspond to silicate frameworks with alkali cation content.

Chemistry and structure

The idealized chemical picture of leucothites involves a framework silicate with aluminum and alkali cations, commonly showing substitutions among Na+, K+, and Ca2+ in the crystal structure. Iron and magnesium can substitute for aluminum in small amounts, and trace amounts of hydroxyl may be present. Leucothites are often described as forming in environments where alkaline, silica-oversaturated fluids interact with rocks, yielding a light-colored, low-density silicate phase.

Occurrence and associations

Leucothites have been reported from alkaline igneous and metasomatic settings, including nephelinite- and phonolite-related rocks, and in pegmatitic pockets within carbonatites. They are typically found with other feldspathoid minerals such as nepheline and leucite, along with calcite and quartz.

Locality and naming

The genus name commemorates the pale appearance, with the type locality associated with the Leucoth Range region. As a relatively recent addition to mineral taxonomy, leucothite references are primarily found in specialized mineralogical databases and descriptive papers.

See also

Leucite, Feldspathoids, Silicate minerals.