sivuviite
Sivuviite is a rare mineral discovered in 1993, named after the Sivunpää mine in Finland where it was first found. It is a complex oxide mineral with the chemical formula Na4Ca2Mn3+3Fe3+2Ti2Si6O24. Sivuviite crystallizes in the monoclinic crystal system and typically forms small, dark brown to black crystals or granular masses. Its hardness on the Mohs scale is approximately 5.5, and it has a specific gravity of around 3.6.
Sivuviite is notable for its unique chemical composition and the presence of both trivalent manganese (Mn3+)
Due to its rarity and the difficulty in obtaining large, well-formed crystals, sivuviite is not commonly used