Ferriakasakaite-(La) and ferriandrosite-(La): new epidote-supergroup minerals from Ise, Mie Prefecture, Japan

Abstract

The new rare-earth element-rich monoclinic epidote-supergroup minerals, ferriakasakaite-(La) (ideally, ^A1Ca^A2La^M1Fe^3+M2Al^M3Mn²⁺(SiO₄)(Si₂O₇)O(OH), Z = 2, space group P2₁/m) and ferriandrosite-(La) (^A1Mn^2+A2La^M1Fe^3+M2Al^M3Mn²⁺(SiO₄)(Si₂O₇)O(OH)), found in tephroite and/or calcite veinlets cutting the stratiform ferromanganese deposit from the Shobu area, Ise City, Mie Prefecture, Japan were studied using electron microprobe analysis and single-crystal X-ray diffraction methods. The two new minerals are rather similar but are distinct by the dominant cation, Ca or Mn²⁺, at A1. This study described these new minerals and examined their crystal-chemical features.