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Crystal structure refinement and Mössbauer spectroscopy of an ordered, triclinic clinochlore

January 1, 1997

The crystal structure of a natural, ordered IIb-4 triclinic clinochlore has been refined in space group C1¯ from 4282 unique X-ray intensity measurements of which 3833 are greater than 3 times the statistical counting error (3σ). Unit cell parameters are a = 5.3262(6) Å; b = 9.226(1) Å; c = 14.334(3) Å; α = 90.56(2)°; β = 97.47(2)°; and γ = 89.979(9)°, which represents the greatest deviation from monoclinic symmetry yet recorded for a triclinic chlorite. The final weighted R is 0.059 for reflections with I > 3σ and 0.064 for all reflections. The chemical formula is (Mg0.966Fe0.034)M1(Mg0.962Fe0.038)M22(Si2.96Al1.04)O10 (OH)2(Mg0.996Fe0.004)M32(Al0.841FeIII0.102Cr0.004Ti0.004)M4(OH)6, which is consistent with electron microprobe (EMP), wet chemical analyses, Mössbauer spectroscopy and X-ray structure refinement. The high degree of ordering of the divalent versus trivalent octahedral cations in the interlayer is noteworthy, with FeIII and Al in M4 and virtually no Fe in M3. In the 2:1 layer, M1 and M2 each contain similar amounts of Fe. The 2 tetrahedral sites have nearly identical mean oxygen distances and volumes, and thus show no evidence of long-range cation ordering.

Publication Year 1997
Title Crystal structure refinement and Mössbauer spectroscopy of an ordered, triclinic clinochlore
DOI 10.1346/CCMN.1997.0450406
Authors Joseph R. Smyth, M. Darby Dyar, Howard M. May, Owen P. Bricker, James G. Acker
Publication Type Article
Publication Subtype Journal Article
Series Title Clays and Clay Minerals
Index ID 70019118
Record Source USGS Publications Warehouse