What is Xonotlite?
Xonotlite is a calcium silicate hydroxide known for white fibrous or radiating aggregates in contact-metamorphic rocks and hydrothermal systems.
Mineralogy and structure
Reference formula: Ca6Si6O17(OH)2. Xonotlite is monoclinic with the ideal formula Ca6Si6O17(OH)2 and can show polytypism. The existing published page is updated in place; COD 9008437 is used as the selected structural reference. Xonotlite is classified with silicates and has monoclinic crystal symmetry. Typical hardness is 6–7 on the Mohs scale and specific gravity is approximately 2.7–2.8.
Colour, lustre and habit
Typical colours include white, colourless, grey, pale pink. The usual fibrous, radiating, massive habit and vitreous, silky, pearly lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Xonotlite forms in or is associated with contact-metamorphic limestones, skarns, hydrothermal veins and cement-related alteration systems. Important documented localities include Tetela de Ocampo in Mexico, Italy, South Africa, Australia and other calc-silicate localities.
White fibres from a calcium-silicate system
Xonotlite is attractive when its fine radiating fibres are preserved. It also links natural skarn mineralogy to cement and low-temperature calcium-silicate chemistry.
Collecting and care
Protect fibrous surfaces from abrasion and dust; avoid acids and retain the host-rock context.
