Here at AGR, we never get tired of seeing zirconia dendrite stones in glass containers. The little snowflake crystals swarm in the middle of a glassy knot enriched in alumina, a bit like dandelion tufts floating in a puddle or a star cluster observed through a telescope. These stones are created when AZS refractories in the melter erode and drip down into the molten glass. Upon cooling, the zirconia recrystallizes (devitrifies) to form the familiar snowflake shapes. The resultant glassy knots and crystals usually have a low amount of stress, but are nevertheless undesirable in glass articles.