Starring Attraction

Here's a jewel from the collection of teenager Sean Green. Sean collects "junk in glass". In this case, an exceptionally large potstone makes this pretty Star signal a unique insulator. How do "rocks" like this get into the glass mix? In some cases foreign objects are introduced into the glass mix through cullet glass, which is nearly always added in the manufacturing process. Sometimes, though, pieces of firebrick from the furnace break off as the bricks wear out. That may be the case here.