Residuum

Residuum is the residue of arcane energy, manifesting as a green dust obtained from whitestone ore that is useful in several magical applications.

Properties
Although not inherently magical, it is particularly receptive to arcane energies and therefore may be used to create objects that retain more powerful enchantments, perhaps for longer periods of time. It can also be utilized to replace and act as other expensive materials and components for spells and other uses. Finally, it is one of two substances that can be refined into the drug suude, which can enhance spellcasting.

Raw residuum can be purified into a dark green glass; in this form it is referred to refined residuum and displays stronger magical properties. When Caduceus placed shards of refined residuum in the forge of the Cinderrest Sanctum, the crystal developed root-like tendrils and its color shifted to purple. Whether this happens generically to residuum glass under intense temperatures or it's a specific property of Melora's sanctuary is unknown.