What is Jasmundite?
Jasmundite is a rare calcium silicate sulfide from high-temperature volcanic and contact environments, with an unusual structure that bridges mineralogy and cement chemistry.
Mineralogy and crystal structure
Reference formula: Ca22(SiO4)8O4S2. Jasmundite has a tetragonal structure containing silicate groups, calcium, oxide and sulfide components. Its unusual chemistry is one reason it is useful in studies of natural and industrial high-temperature phases. Jasmundite is classified with silicates and has a tetragonal crystal system. Typical hardness is 5–6 on the Mohs scale and specific gravity is approximately 2.9–3.1.
Colour, lustre and habit
Typical colours include brown, black, red-brown. The usual granular, prismatic, massive habit and vitreous, sub-metallic lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Jasmundite forms in or is associated with high-temperature volcanic slags, skarns and calcium-rich silicate assemblages. Important documented localities include the Bellerberg volcano region in Germany and other high-temperature calcium-silicate localities.
An unusual high-temperature mineral for a serious cabinet
Jasmundite rewards collectors who want a specimen with a genuinely unexpected formula. Its dark appearance contrasts with a calcium-silicate-sulfide framework that connects volcanic mineralogy with the chemistry of clinker-like materials.
A specimen with an origin story
High-temperature minerals are often appreciated as records of transformation, pressure and heat. That symbolism is a personal reading; Jasmundite's documented structure and Bellerberg setting provide the stronger, evidence-based narrative.
Collecting and care
Protect small crystals and avoid aggressive cleaning; retain the matrix because the geological context is part of the identification.
