Residuum

The residue of arcane energy, manifesting as a green dust obtained from whitestone that is useful in several magical applications.
Although not inherently magical, residuum 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 is used in the amplification of various forms of arcana. 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.
If a spell has a component cost that consumes the component, its caster can substitute the required component for an amount of residuum of an equal value. One pound of pure residuum is worth approximately 500 sp in most markets, though it becomes extremely expensive and difficult to find outside of Emon or the city of Whitestone itself.
Residuum can also be heated and blown into glass, forming a shimmering, greenish surface. Residuum slates or orbs can be used in stationary enchanting tables. Archmages willing to pay exorbitant rates—easily 20,000 sp or more—may acquire an enchanting slate that can be used to expedite the creation of all magic items. Using such a table allows anyone crafting a magic item to do so in one-quarter of the usual time.