Not sure of the maker but there is some neat physics captured within this marble........simple from a distance but upon a closer look, delicately complex.

Thanks for looking, Bill.  

I look at the almost perfectly parallel strata and wonder how and at what point in the process of making a machine made mib, they could form. Reminds me of a Pelt slag. Maybe it is related to glass composition with different glasses separating into strata as the marble cools? Maybe when the glass components have widely different physical properties, like immiscible liquids?