Magnetic properties of sheet silicates; 2:1:1 layer minerals

Ballet, O.; Coey, J. M. D.; Burke, Kieron

doi:10.1007/bf00654348

Cited by 83 publications

(29 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The apparent single Fe 2+ doublet must consist of unresolved doublets due to Fe 2+ in M(1) and M(2) of the 2:1 layer and M(3) of the interlayer sheet. Support for this interpretation comes from Mrssbauer spectral studies of several Febearing chlorites by Ballet et al (1985) and Townsend et al (1986). Both sets of authors found they could not distinguish Fe TM ions in cis and trans octahedral sites of the 2:1 layer and in octahedral sites of the interlayer sheet.…”

Section: Octahedramentioning

confidence: 91%

Refinement of the Crystal Structure of A Monoclinic Ferroan Clinochlore

Rule¹,

Bailey

1987

Clays and clay miner.

View full text Add to dashboard Cite

Abstract--A monoclinic IIb-2 clinochlore from Washington, D.C., contrary to previous studies, is primarily a ferroan rather than a ferrian chlorite. Disorder of tetrahedral Si,A1 cations is indicated because of unsuccessful structural refinements in subgroup symmetries. The true space group is C2/m. Slight ordering of Mg, Fe 2+, and Fe 3+ over octahedra M(1) and M(2) within the 2:1 layer (mean M-O,OH = 2.092 and 2.084 A, respectively), complete ordering of trivalent A1 into the centrosymmetric octahedron M(4) of the interlayer sheet (M-OH = 1.929 ,~), and ordering of primarily divalent cations (Mg and Fe) into the two interlayer M(3) octahedra (M--OH = 2.117 ~) exist. The excess of negative charge above unity due to tetrahedral substitution of A1 for Si (1.378 atoms) is compensated entirely within the octahedral sheet of the 2:1 layer.Ordering of a trivalent cation into one octahedron in the interlayer should be universal for all stable trioctahedral chlorites. In this specimen the ordering is due to (1) minimization of cation-cation repulsion by layer offsets which provide more space around the trivalent element, and (2) energy minimization by localization of the source of positive charge on the interlayer sheet in one octahedron rather than two. In other structures or for different compositions additional factors can be important also. Most chlorites of the IIb and Ib (fl = 90 ~ types are expected to show disorder of the tetrahedral cations. The b positioning of interlayer and layer provides no preferential driving force for concentration of Si and A1 in any tetrahedron as a consequence of the expected ordering of the interlayer cations. The monoclinic IIb-2 polytype is less abundant in nature than the triclinic IIb-4 and IIb-6 structures, because only half as many possible superpositions of layers exist that will produce monoclinic symmetry. Crystallization factors must also be important, because the IIb-2 chlorite is much less abundant than predicted by this purely geometrical argument.

show abstract

Section: Octahedramentioning

confidence: 91%

Refinement of the Crystal Structure of A Monoclinic Ferroan Clinochlore

Rule¹,

Bailey

1987

Clays and clay miner.

View full text Add to dashboard Cite

show abstract

“…Hence, the easy direction lies in the plane. 6 is positive (30 K) and, from Eq. [14][15][16][17][18][19][20], the exchange constant is J = l.25 K, counting only the six neighbors in the plane.…”

Section: -58 Other Mineralsmentioning

confidence: 96%

“…The susceptibility and magnetization are calculated by summing over the energy levels, weighting each by its Boltzmann factor, viz., 6 I m i exp (-E/kT) i= 1 <m> = 6 I exp (-E. IkT)…”

Section: -21 Susceptibility and Magnetization Of Iron(iii)mentioning

confidence: 99%

Magnetic Properties of Iron in Soil Iron Oxides and Clay Minerals

Coey

1988

Iron in Soils and Clay Minerals

Self Cite

View full text Add to dashboard Cite

“…Further, trivalent cations tend to concentrate into the smaller M4 site. If the cations are disordered over the 2 sites, the symmetry can be monoclinic, whereas ordering of trivalent cations into M4 causes a difference (D) in the mean cation oxygen dis- (Taylor et al 1968;Coey 1975;Ericsson et al 1977;Goodman and Bain 1978;Blaauw et al 1980;Borggaard et al 1982;Kodama et al 1982;Ballet et al 1985;Raclavsk~i and Raclavsk# 1988;Aramu et al 1989;Christofides et al 1994) that are generally assigned to the M1 and M2 sites, but are recognized to be potentially indistinguishable from M3 and M4 doublets. In many of these studies (for example, Christofides et al t994), the authors were primarily interested in Fe(IU)/Fe(II) ratios, and so did not pursue more elaborate fitting schemes to determine Fe occupancy of the interlayer sites.…”

Section: Introductionmentioning

confidence: 99%

Crystal Structure Refinement and Mössbauer Spectroscopy of an Ordered, Triclinic Clinochlore

Smyth

Dyar

May

et al. 1997

Clays and clay miner.

View full text Add to dashboard Cite

Abstract_---The crystal structure of a natural, ordered llb-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 (3~). Unit cell parameters are a = 5.3262(6) ,~; b = 9.226(1) A; c = 14.334(3) ,~; c~ = 90.56(2)~ [~ = 97.47(2)~ and ~/ = 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 > 3(r and 0.064 for all reflections. The chemical formula is (Mgo966Fe0034)Ml(Mg0%2Fe0038)M22(Si296Alt04)Ot0 (OH)2(Mg0996Fe0.004)M32(A10841Fen~0102Cr00o4Ti00o4)M4(OH)6, which is consistent with electron microprobe (EMP), wet chemical analyses, Mrssbauer spectroscopy and X-ray structure refinement. The high degree of ordering of the divalent versus trivalent octahedral cations in the interlayer is noteworthy, with Fetn and A1 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.

show abstract

Magnetic properties of sheet silicates; 2:1:1 layer minerals

Cited by 83 publications

References 13 publications

Refinement of the Crystal Structure of A Monoclinic Ferroan Clinochlore

Refinement of the Crystal Structure of A Monoclinic Ferroan Clinochlore

Magnetic Properties of Iron in Soil Iron Oxides and Clay Minerals

Crystal Structure Refinement and Mössbauer Spectroscopy of an Ordered, Triclinic Clinochlore

Contact Info

Product

Resources

About