Great notes, whomever wrote that!

One thought: can you get layers like that in basalt as a result of multiple flow events or spattering or something.

I'm thinking, imagine a chunk that's on the interior wall of a lava tube. It cools, another pulse of lava comes down, a thin layer solidifies along the walls. Then another one. Thus you get layers even though it's pure igneous basalt.

You can also get some really wierd, rounded and smoothed forms in lava tubes due to hot gases flowing through them, melting and softening the walls. "Lava-cicles", even.

Or, something that was close to a vent -- or a spatter cone or pressure ridge or something, where there was time for some blobs to be extruded, cool somewhat, and then have more lava stuck on.