My friend has a campsite by a the river. He noticed these white chunks that seem to be knappable. He called it white obsidian. Thick, white, will throw a spark! but knaps well.
Get this, there is a factory maybe a half mile from there. They make correll plates. I think it may be some material discarded by the factory. Like excess, possibly contaminated porcelain or glass.
I'll try to get some for pics to keep ya posted. Wondering if anyone else has come across anything like it./