| Reference Type | Journal (article/letter/editorial) |
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| Title | Cation and anion substitutions in the humite minerals |
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| Journal | Mineralogical Magazine and Journal of the Mineralogical Society |
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| Authors | Ribbe, P. H. | Author |
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| Gibbs, G. V. | Author |
| Jones, Norris W. | Author |
| Year | 1968 (September) | Volume | 36 |
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| Issue | 283 |
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| Publisher | Mineralogical Society |
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| Download URL | https://rruff.info/doclib/MinMag/Volume_36/36-283-966.pdf+ |
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| DOI | doi:10.1180/minmag.1968.283.036.08Search in ResearchGate |
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| Generate Citation Formats |
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| Mindat Ref. ID | 6189 | Long-form Identifier | mindat:1:5:6189:0 |
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| GUID | 0 |
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| Full Reference | Ribbe, P. H., Gibbs, G. V., Jones, Norris W. (1968) Cation and anion substitutions in the humite minerals. Mineralogical Magazine and Journal of the Mineralogical Society, 36 (283) 966-975 doi:10.1180/minmag.1968.283.036.08 |
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| Plain Text | Ribbe, P. H., Gibbs, G. V., Jones, Norris W. (1968) Cation and anion substitutions in the humite minerals. Mineralogical Magazine and Journal of the Mineralogical Society, 36 (283) 966-975 doi:10.1180/minmag.1968.283.036.08 |
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| In | (1966) Mineralogical Magazine Vol. 36 (283) Mineralogical Society |
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| Abstract/Notes | SummaryThe humites are structurally analogous to olivine wherein the replacement of four oxygen by four (F,OH) anions in the slightly distorted, hexagonal close-packed array is balanced by the replacement of one tetrahedrally coordinated Si by a tetrahedral void, according to the general formula Mg2xSix-1O4x-4(F,OH)4 where x = 3, 5, 7, 9. In humites the key structural units are not ‘olivine and sellaite (or brucite) layers’, as previously assumed, but are zigzag chains of edge-sharing octahedra, just as in olivines. It is shown that for humites and olivines alike the unit cell parameters a, b, and d001/n and the cell volume (normalized to one-half the mean anion-anion distance along the normal to (001)) vary linearly with the average radius of the octahedrally coordinated cation in the chain.Substitutions of (F,OH) for O and vacancies for Si have second-order effects on the unit cell parameters, causing a linear decrease of the normalized cell volume with increase in F/O ratio in the synthetic series forsterite-humite-norbergite. Comparison of the crystal structures of forsterite and norbergite shows that the polyhedral distortions in norbergite are smaller than in forsterite in accord with the decreased number of shared edges: the fluorines in norbergite are bonded to three Mg atoms whereas all anions in forsterite are bonded to three Mg and one Si atom. |
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