Ganophyllite
A phyllosilicate named in 1890 from the Greek for 'leaf' and 'luster' — after its lustrous cleavage surfaces.
Intro adapted from Wikipedia (CC BY-SA).
Ganophyllite is an IMA-recognized mineral species in the silicate class, with the chemical formula (K,Na)ₓMn²⁺₆(Si,Al)₁₀O₂₄(OH)₄·nH₂O (x = 1-2; n = 7-11).
It crystallizes in the monoclinic crystal system (space group A2/a). It is a member of the Clay structural group.
Key properties: Mohs hardness 4–4.5; specific gravity 2.77–2.84; Vitreous, brilliant. Color: Light brown, pale pink luster; optically biaxial.
IMA symbol Gnp, grandfathered status — known before the IMA’s founding, named in 1890.
Found in manganese-rich portions of metamorphosed Zn-Mn mineral deposits.
It is found associated with Calcite, rhodonite, caryopilite, barite, lead, garnet, manganoan biotite, pyrophanite (Harstigen mine, Sweden); rhodonite, willemite, bustamite, axinite.
Its name comes from the Greek for luster and leaf, for the high luster on cleavages.