Defects in glass formation occurring due to poor placement of fiber type refractory materials.

A thin section of an Alumino-Silicate stone shown in a polarizing microscope.

A very “organic” display of mechanical damage caused by glass to glass contact. The vertical frictive track exhibits crescent shape cracks leading up to a wing-like contact bruise.

A type of inclusion observed in pharmaceutical glassware typically referred to as "slag eye".