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Stylolites. On one of the two limestone vertical slabs in the Mens Room on the east side of Veihmeyer, between the southeast entrance and the elevator/stairs. It’s a strange little room — you go down a set of stairs into this cramped space and there are the stylolites staring you in the face.

This rock is a limestone, which is composed almost entirely of one mineral, calcite, which has the formula CaCO3. This limestone was buried deeply enough that it started to dissolve under the pressure. The little bits of insoluble material, like organic matter and clay, get left behind and are concentrated along the places where the rock was dissolved. The jagged black lines clearly mark the areas where most of the dissolution occurred and are called stylolites.

Geology.
It's everywhere.