tsilaisite

Tsilaisite is a mineral with the chemical formula NaCaMgSi6O15(OH)·H2O. It is a rare silicate mineral that was first discovered in the Tsilaizina pegmatite in the Malagasy Republic (now Madagascar). The mineral was named after the locality where it was found. Tsilaisite belongs to the amphibole group of minerals, characterized by its double-chain silicate structure. Its physical properties include a vitreous luster and a hardness of approximately 5 on the Mohs scale. It typically appears as prismatic crystals and can range in color from colorless to pale yellow or green.

The geological occurrence of tsilaisite is primarily associated with complex pegmatites, which are igneous rocks characterized by their exceptionally coarse grain size. These pegmatites are often rich in rare elements. Tsilaisite has been found in association with other rare minerals within these formations. Its rarity means that detailed studies on its formation and geological significance are limited. Research on tsilaisite often focuses on its crystallography and chemical composition to understand its place within the complex mineralogy of pegmatite environments.