Mayco Jungle Gems Crystal Glaze - CG 786 - Obsidian - 4 Ounce Jar Jungle Gems burst into color and intricate pattern during the firing process. Jungle Gems can be used in a combination with other glazes, by themselves, or simply as accent to a design. Fire to shelf cone 06, or to shelf cone 05 if more flow is desired. AP Certified Non-Toxic. with the exception of CG 707 Woodland Fantasy and CG 713 Peacock Green which require a caution label, CL, due to soluble copper. Made in USA.