I π― % agree with cheese , imho without having dug at the sites and examined bags with providence. The marble companies in that area that made swirls lots of them shared product cullet from my research, and glass will do pretty much the same thing with a sheer and some rollers. That's is why I think some swirls are gonna be almost impossible . I'm just a few years old so I could be off....
Well I am off quite a bit , and missing a few marbles...π€ͺ