On the Nature of Co-Ni Asbolane; a Component of Some Supergene Ores

Abstract

Co-Ni asbolane specimens from the Lipovsk and Tyulenevsk deposits in the Middle Urals and from Buranovsk deposit in the South Urals were examined by analytical electron microscopy. Chemical analyses are also given. Most suitable for a detailed examination was Co-Ni asbolane from the products of weathering of the Lipovsk serpentinites. Thus, a study of Co-Ni asbolane from the Lipovsk deposit has shown that the mineral has a hybrid structure composed of the layers of Mn⁴⁺ and Co-Ni octahedra alternating along c axis. These layers form hexagonal sublattices I and II with parameters (under vacuum) a = 2.823, c = 9.34 Å (Mn⁴⁺ sublattice), a = 3.04 Å and c = 9.34 Å (Co-Ni sublattice). In the layers of different types the octahedra differ in azimuth orientation as much as 60°. The chemical formula of the Lipovsk asbolane may be written as

$$ {\left[ {M{n^{{4 + }}}{O_{{2 - x}}}{{\left( {OH} \right)}_x}} \right]^{{x + }}}{\left[ {R_{{1 - y}}^{{2 + }}{{\left( {OH} \right)}_{{2 - 2y + x}}}} \right]^{{x - }}} $$

where: R²⁺ is Ni, Co, Ca; x and y < 1. Both electrostatic and hydrogen bonds exist between the layers of different types.