Eclogitic pyroxenes, ordered with P2 symmetry

J. R. Clark; J. J. Papike

doi:10.1126/science.154.3752.1003

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Eclogitic pyroxenes, ordered with P2 symmetry

J. R. Clark·J. J. Papike

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Abstract

X-ray diffraction crystal-structure analysis of omphacite from eclogite, Tiburon Peninsula, Marin County, California, shows that this clinopyroxene has P 2 symmetry with a nearly ordered distribution of the multiple cation content defined by its approximate formula: (Na 0.5 Ca 0.5 ) (Mg 0.4 Fe 2 + 0.1 Al 0.4 Fe 3 + 0.1 )Si 2 O 6 . Na+ and Ca 2+ tend to assume alternate locations in the structure, and (Mg,Fe 2+ ) octahedra alternate with Al 3+ or (Al,F 3+ ) octahedra in chains along c .

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Source-reported bounding extent: 37.859632189213315° to 37.90942740343871° latitude; -122.49955325240819° to -122.43309025534263° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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J. R. Clark, J. J. Papike. 1966. Eclogitic pyroxenes, ordered with P2 symmetry. https://doi.org/10.1126/science.154.3752.1003

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