Can confirm. I've walked on a dirt floor that was hard as rock, and nearly as smooth as glass. No dust on it either. The dirt apparently had a high clay content in it (guessing by look, feel, and texture) and after years of being walked on like that, it looked and felt like walking on a smooth ceramic surface.

(Edit). On a side note, I've also seen house walls made of mud that are still in perfectly good shape to this day, nearly 200 years after the house was built. Pretty amazing to see.