What the Pumice Did

I wasn't shocked- I've always imagined pumice as a sort of aerated glass/rock combo. Next to the rather nice grey melty test tile [pumice powder] is a piece of glass someone gave me, supposedly from a volcano...I suppose the next step would be to fire it on a vertical surface to see if it runs- if not,I'd probably use it straight as a glaze, probably on some porcelain, probably on a shape I'd dream up to show off its particular charms- I wonder what that'd be...