A new 14 Å mineral of the birnessite group in deep-sea micronodules

Abstract

EXPERIMENTS by Feitknecht and Marti¹ and more recently by Giovanoli et al. have shown that oxidation of Mn(OH)₂ in NaOH solution gives rise to a Na-buserite. Drying Na-buserite converts it to Na-birnessite. If a solution of a calcium salt is shaken with Na-buserite the latter is transformed into pseudo-hexagonal Ca-buserite, characterised by a basal spacing of 10 Å. After drying this spacing is reduced up to 7 Å and buserite is converted into Ca-birnessite. We describe here a new natural Ca-bearing member of the birnessite group of unit cell parameters comparable with those of a synthetic compound described² as Na–-Mn (p, m) manganate, belonging to the birnessite group. In ASTM (23–1046) this substance is called Na-birnessite.