An edingtonite crystal from Ice River, British Columbia, Canada, has a clear, euhedral rim and whitish, anhedral core. The rim shows the m{110}, o{111}, p{111}, and c{001} sectors and a small 2V value (about –22°) with some exceptions in the {111} sector, and the core shows twinning without sectors and a large 2 V value (about – 52°). X-ray diffraction analysis indicated that both the core and the rim are orthorhombic. However, optical observation leads to a different conclusion: the core is orthorhombic and consists of an ordered Al-Si structure, whereas the rim, especially the {110} sector, is evidently triclinic and has a partly ordered structure.

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