Abstract
Chlorite has a structure composed of a combination of two distinct layers, the tetrahedral15
octahedral-tetrahedral (TOT) and the interlayer (i.e. the octahedral layer between TOT layers).
In this study, the morphology and dissolution of chlorite in pure water has been visualized
using Atomic Force Microscopy. Upon cleavage, the TOT layer shows atomically flat
terraces and steps, while the interlayer presents strips and voids. In pure water, dissolution
channels and equilateral, mono-oriented triangular etch pits form in the interlayer and lead to
progressively increased solubilisation. Dissolution channels are proposed to originate from
structural defects, while a conceptual model is discussed to explain the presence of triangular
etch pits. In this model, their formation is driven by the different reactivity of the two
octahedral configurations along the etch pits. It is not currently known which of these is the
most stable configuration, however we propose arguments that point towards a specific
orientation. The conceptual model is supported by experimental data and is potentially
applicable to all mineral structures constituted by continuous octahedral layers.
