Litharenite

Litharenites are sandstones that contain less than 75% quartz and in which the ratio of unstable rock fragments to feldspars is greater than 3:1.

The photos above (crossed polarizers on the left, plane polarized light on the right) show a rock consisting almost entirely of subrounded andesite grains, with minor chalcedony cement. The photo below, under crossed polarizers, shows dark basalt clasts, olivine and plagioclase mineral fragments in a matrix of chlorite and calcite.



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