Aenigmatite
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Aenigmatite, also known as cossyrite after Cossyra, the ancient name of Pantelleria, is a sodium, iron, titanium inosilicate mineral. The chemical formula is Na₂Fe²⁺₅TiSi₆O₂₀ and its structure consists of single tetrahedral chains with a repeat... Wikipedia
Crystal class: Pinacoidal (1); (same H-M symbol)
Crystal habit: Poorly developed prismatic crystals, occurring as irregular clusters; pseudomonoclinic
Crystal system: Triclinic
Formula (repeating unit): Na2Fe2+5TiSi6O20
Optical properties: Biaxial (+)
Space group: P1