The Source
The named metal of the light school — the reagent of drown-glass, hold-the-line, and sky-tear, and the one the anvil-singers set in the masterwork's fuller.
The Yield
A seam gives a year for a reagent's worth; a reagent's worth gives the answer.
In the Workshop
The silver is the reagent of the answer: the light is the answer, not the question, and the silver is the one the answer is spent on — the named metal is the named price.
Cost band: master (the reagent grade) — on the ladder in The Maker's Hand, the material is the floor, and the floor is the one the mine or the marsh or the tree has to give. Recipes that take it: runecraft, alchemy, the light school's reagent spells