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induration, by weathering

 
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Plate VI. Thin sections of quartzite.
Fig. 1 (upper half). Huronian quartzite from gannister quarry, south side of Carp River, near Marquette, Mich. No. 22 of the list, p. 28. Polarized light. Enlarged 31 diameters.
Fig 1. (lower half). Huronian quartz-schist from near Marquette, Mich. No. 27 of the list, p. 29. Polarized light. Enlarged 36 diameters. Designed to show schistose structure and induration by independently oriented quartz.

Thin sections of quartzites in which the fine interstitial quartz is present are not easily represented by figures. At the lower half of Fig. 1, Plate VI, an attempt is made.... (p 17)

Figures (cropped from black surround) illustrating Roland Duer Irving (1847-88 *) and Charles Richard Van Hise. On secondary enlargements of mineral fragments in certain rocks. Bulletin of the USGS. No. 8. 1884.
 

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tags: R. D. Irving; C. R. Van Hise; induration; polarised light; rounds; weathering