Miscellany | Published:

Geological Notes

Nature volume 30, pages 201202 | Download Citation



TRICLINIC PYROXENE.—Mr. J. J. Harris Teall points out to us that since the paper was written on this subject by Mr. Whitman Cross, to which reference was made in NATURE (ante, p. 155), this author has found that, after reconsidering the matter in the light of the researches of Fouqué and Michel Lévy on the optical properties of monoclinic pyroxene, a great majority of the instances cited by him as indicating a triclinic pyroxene are explainable as augite, and that the few cases which still seem anomalous are not in themselves sufficient to justify a reference to the triclinic system. The mistake was made in specimens not cut rigidly parallel to the axis, for it appears that the ellipsoid of elasticity is so situated as to produce very great variations in optical behaviour in sections which are but little inclined to each other. [Amer. Journ. Science, No. 151, xxvi. p. 76].

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