TIN (Stannous chloride): Fine white powder used as dye mordant circa 5000 BC in Egypt; Africa circa 900 BC; Greece circa 50 BC. No record of use in pre-1600 Europe, but this needs much more research. Just a pinch brightens colors; too much makes wool brittle. Best on wool, silk, mohair.
There is currently a world-wide shortage of tin, to the point that there are reports of people panning streams to find some. Unfortunately, the extremely low supply is reflected in the new price for tin.
HISTORY NOTE: Unsuccessful physicist mathematician Cornelius Drebbel announces discovery of cochineal red with tin mordant in 1630 AD. His claim doubted in 1938 CIBA Review; tin mordant used in 50 AD Greece.