Pot stones' are simply larger pieces of eroding furnace brick becoming suspended in the glass. Pot stones the size of a dried pea are usually significant enough to always cause a fracture during cooling. Just one little fleck of rust or scrap iron causes a nice amber streak when poured. If rusty steel or iron ladles were used to pour insulators, rust flecks would be left in the glass tank after each time the ladle was dipped in. These flecks would melt and make little regions of dark green glass waiting for the ladle to come back and scoop them up for the next pour.
Iron oxide is one of the oxides used for coloring glass green.
When we refer to amber streaking in glass, it's usually this iron oxide green that we see. A little TSP in aqua glass would result in the 'Jade Milk' Hemingray products. Tiny 'seed' bubbles are the result of incomplete glass ingredient melting. The alkali which dissolves the silica in the melting action creates small gas bubbles. These bubbles take a long time to rise to the surface and pop, and usually become suspended in the molten glass.