Aetherium

Aetherium is the name given to an elemental powder produced when magical spells are cast. While invisible to the naked eye and completely intangible, it can be seen by use of the Detect Magic spell as created by Plint the Young. Aetherium manifests around the magical Event Point(s) at the moment a spell is cast, which can vary depending on the specific spell. For example, a Druidcraft spell used to light a candle will cause Aetherium traces along the caster's fingertips, from the somatic component of the spell; along the caster's lips, from the verbal component, and along the tip of the candlewick, where the spell was cast. On the other hand, a spell such as Comprehend Languages that targets only the caster, will only manifest Aetherium on the fingers and lips of the caster, where verbal and somatic components are present. The Comprehend Languages spell also requires a material component, as do many spells. When the spell is cast with this component present, often in the hand of the caster, it is completely erased from the plane the caster is on. It's shape is mimicked by Aetherium for a brief moment, before falling to the ground as dust.

As Aetherium is theorised to be not of this world, it soon breaks down at a steady rate. This decay gives off a form of energy referred to as Magirad, which is measured in units of the same name. This Magigrad energy passes through most non-magical objects on the material plane, though some studies suggest that it can be harmful to living tissue when on the Astral plane.

Forms of Aetherium
The schools of magic are defined by which precise isotopic form the Aetherium takes. From this difference, it is possible to determine which school of magic a spell was from after it has been cast. The 'level' of the spell, or how much magical energy it takes to cast, can also be determined by it's form as each form will break down at a different rate, though this does require a timeframe. The Aetherium trace left by a Level 2 Abjuration spell after 21 hours will have an identical Magigrad level to a level 1 Abjuration spell the moment it is cast.