Nanostructure of palygorskite/sepiolite in Texas caliche: Possible bacterial origin

In a caliche from west Texas, watermelon-shaped calcite crystals are coated with fibers of palygorskite/sepiolite clay, which also extend out into pore spaces as spiky filaments. Some filaments are smooth and capped by ovoid 30–100nm beads. Other filaments are made of rosary-like chains of beads. Th...

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Bibliographic Details
Published in:Carbonates and evaporites 2007-09, Vol.22 (2), p.113-122
Main Authors: Folk, Robert L., Rasbury, E. Troy
Format: Article
Language:English
Subjects:
Beads
Calcite
Caliche
Cell walls
Clay
Clay minerals
Coatings
Crystals
Fibers
Filaments
Gold coatings
Minerals
Palygorskite
Sepiolite
Water melons
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Summary:In a caliche from west Texas, watermelon-shaped calcite crystals are coated with fibers of palygorskite/sepiolite clay, which also extend out into pore spaces as spiky filaments. Some filaments are smooth and capped by ovoid 30–100nm beads. Other filaments are made of rosary-like chains of beads. These objects are seen both in gold-coated and carbon-coated samples, thus are not artifacts. We suggest that these minute features were cells of nannobacteria (dwarf forms) that precipitated the clay filaments, in a similar manner as larger bacteria that accumulate clay minerals on their negatively-charged cell walls.
ISSN:0891-2556
1878-5212
DOI:10.1007/BF03176241