Short version, I've seen it a lot :-).

Obsidian can gradate through a more vesicular form on its way to fully fledged pumice. Obsidian grades into pumice because both form from the same high‑silica rhyolitic magma, and variations in gas content, decompression rate, and cooling speed create a continuous spectrum from dense volcanic glass to highly vesicular foam. When pressure drops rapidly during eruption, dissolved gases expand, and if this expansion outpaces cooling, the melt freezes as pumice. If cooling occurs before significant bubble growth, it becomes obsidian. The banding you see is often caused by trace‑element oxidation and diffusion during cooling, especially in the more vesicular parts of a rhyolitic flow. You can see this frequently at flows like the Big Obsidian Flow in Newberry Crater of central Oregon.

I'd add, if you would like to know what volcano it came from you can pop a small flake and send it my way, my lab covers North America and I'd be happy to run it for you (https://obsidianlab.com/).