Crystal Chemistry of Corrensite: A Review

Abstract

Abstract--Statistical analyses of chemical data from the literature of corrensite minerals suggest a large compositional variability, more evident in octahedral than in tetrahedral coordination. Mg occupies 40-80% of the octahedral sites, with A1 and Fe 2+ making up the remainder. Approximately 15-30% of the tetrahedral sites are filled by A1. Despite this compositional variability, distinct fields for the several types of mixed-layer trioctahedral chlorite/trioctahedral swelling layer are not apparent. Statistical analyses of the composition of corrensite compared with saponite, vermiculite, and chlorite suggest that corrensite is an intermediate between trioctahedral chlorite and trioctahedral smectite. If Fe/(Fe + Mg) > 50%, chlorite alone is favored, but with increasing Mg, chlorite appears to transform into corrensite and then, by iron oxidation, into trioctahedral smectite. Despite the chemical variability between corrensite, chlorite, and saponite, corrensite appears chemically to be a well-defined species. On the other hand, corrensite cannot be characterized chemically on the basis of its swelling component. Thus, the current definition of corrensite as a regular 1:1 interstratification of trioctahedral chlorite and either trioctahedral smectite or vermiculite is appropriate.

Chlorite, Corrensite, and Chlorite-Mica in Late Jurassic Fluvio-Lacustrine Sediments of the Cameros Basin of Northeastern Spain

“…analyses. Examples of corrensites where K is a major component were reported by Brigatti and Poppi (1984), Shau and Peacor (1992), and Jiang and Peacor (1994a). Muscovite within the chlorite-mica crystals has significant Ti and relatively low Na and Ca contents.…”

Chemiographic Analysis of Trioctahedral Smectite-to-Chlorite Conversion Series from the Ohyu Caldera, Japan

“…The maximum amount ofoctahedral vacancies (the boundary of the solid solution toward the 4Si pole) was constrained to that shown by brunsvigite from Silent Valley ( Figure 1, point b; Deer et al, 1971). Compositions of trioctahedral vermiculites (de la Calle and Suquet, 1988) are plotted in order to analyze the compositions of the ordered chlorite-vermiculite (i.e., high-charge corrensite) compiled by Brigatti and Poppi (1984).…”

“…Data from Brigatti and Poppi (1984) are used to illustrate the usefulness of the M+-4Si-3R 2 § diagram. When plotted, the data suggest that corrensite has a broad chemical composition field (Figure 1).…”

“…This means that the chlorite-to-smectite ratio in the corrensite must not be very different from unity since the intensity and the sharpness of the superlattice reflection should decrease markedly were this not the case (Reynolds, 1988). Figure 1 shows that the compositions compiled by Brigatti and Poppi (1984) do not correspond to pure corrensite but to mixtures of corrensite with a discrete trioctahedral expandable clay (e.g., saponite, stevensite, vermiculite) or chlorite.…”

Corrensite of Hydrothermal Origin from Veitsivaara, Eastern Finland

“…B a n d s near 820 a n d 760 c m -1 in . Triangular plot of octahedral occupancy for corrensite from Veitsiv~ara and data from Brigatti and Poppi (1984a) and Morrison and Parry (1986).…”