Is this cupro or rayon? Cant tell from the drape

Picked up this fabric at a thrift store -- no content label, obviously. It has a really fluid drape, almost like sand-washed silk but way too cheap for that. Cool to the touch, doesnt wrinkle easily. I tried a burn test and it melted slightly then self-extinguished, so maybe rayon or a rayon blend? Has anyone had luck identifying mystery thrift store fabrics? The burn test is helpful but Im never 100% sure.