Cone 06: Plum Jelly is a translucent purple base glaze with white crystals that bloom and a variety of white and blue specks. Base glaze fades to blue – crystals fade and melt. Enhanced mobility. Jungle Gems™ Crystal Glazes transform in the kiln when the small pieces of glass frit burst into color and intricate patterns during the firing process. Artists use these beautiful glazes to add dramatic, colorful effects to their creations.