• journal_title：Clays and Clay Minerals
• Contributor：Åsa Zazzi ; Tomas K. Hirsch ; Ekaterina Leonova ; Andrei Kaikkonen ; Jekabs Grins ; Hans Annersten ; Mattias Edén
• Publisher：Clay Minerals Society
• Date：2006-
• Format：text/html
• Language：en
• Identifier：10.1346/CCMN.2006.0540210
• journal_abbrev：Clays and Clay Minerals
• issn：0009-8604
• volume：54
• issue：2
• firstpage：252
• section：Articles

The structures of one synthetic and two natural chlorites of the chlinochlore type were explored using X-ray diffraction, magic-angle spinning nuclear magnetic resonance (NMR) and Mössbauer spectroscopy. Rietveld refinements indicated that all structures are of the trioctahedral ordered IIb polytype. Mössbauer spectra provided the ratio ^IIFe/^IIIFe but gave no evidence for the presence of ^IIIFe in the brucite-like sheet. We also report unit-cell parameters, Mössbauer isomeric shifts, ²⁹Si NMR chemical shifts as well as ²⁷Al isotropic shifts and quadrupolar coupling parameters. Very broad ²⁹Si NMR peaks from the natural samples prevented us from obtaining accurate information on the Si-Al ordering in the tetrahedral sheets; the limitations of ²⁹Si NMR as applied to natural chlorites are discussed. High-resolution 3QMAS NMR resolved the ²⁷Al signal of the M4 octahedral site in the brucite-like sheet from the other three Al signals of crystallographically inequivalent octahedral positions.