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An Analcite-bearing Tuff in the Carboniferous Limestone of Derbyshire
Published online by Cambridge University Press: 01 May 2009
Extract
In the course of a recent study of the microscopic characters of the pyroclastic rocks of Derbyshire, a colourless, isotropic mineral, with refractive index considerably lower than that of the balsam, was noted in a thin section of a tuff from Cressbrook Dale. The rock consists essentially of a mass of lapilli containing much yellowish basaltic glass, often partially devitrified, and many felspar laths, sometimes with straight extinction, in a cement partly of calcite, and partly of amorphous, opaque material, white or grey by reflected light, which is probably decomposed volcanic detritus, of the same nature as the “toadstone-clays” of Derbyshire. Vitro-clastic structure is abundant.
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References
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