
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.

Petrography
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