Affinity

All mages have what is called an Affinity. This is a quantifiable ability above and beyond the average with certain Forms. It is possible and not uncommon to have two Affinities, although it is rare indeed to find mages with three or more. Affinities are recognizable from the end of The Change onwards, although long study might make them indistinguishable from experience.
Affinities cause small physical or mental changes that can be detected and measured. For example, humanoids with brown eyes are more likely to have Earth or Health as an Affinity. A Tester (as such people are called) can detect even minute details about a person's eyes or temperament to effectively diagnose Affinities.

Manifestation

Physical and behavioural changes can indicate Affinity, although the untrained eye might not necessarily pick these out.

Type

Metaphysical, Arcane