Polished slab of phylloid algal limestone

Typical Pennsylvanian phylloid (meaning "platy") algal limestone. This
kind of limestone is often referred to by the tongue-in-cheek name
"potato chip rock." Although making up only about 15% of the rock
volume, most of the algal plates are in mutual contact so the "pile"
would not collapse if the matrix were removed. When they collected on
the sea floor they created sheltered space for accumulation of the
micritic matrix. These plates were probably washed a short distance
to their final resting places by current action, along with the several
brachiopods visible here that lived among the algae.

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