What It Actually Is

Borax is identified as a hydrated sodium borate, usually given the formula Na2B4O7.10H2O, an identification well confirmed by modern mineralogical and chemical analysis and consistent with every historical description of its source, appearance and flux behavior. Its chief historical significance for the later development of chemistry is that borax's own name gave rise to the name of the element boron, isolated as a distinct element only in 1808 by Humphry Davy and, independently, by Joseph Louis Gay-Lussac and Louis Jacques Thenard, meaning that, exactly as with aluminium and alum or zinc and calamine, borax was mined, traded and used skillfully for centuries before the element responsible for its most useful properties was recognized and isolated on its own.

There is no real scholarly dispute over borax's modern chemical identity; the interest here again lies in how consistently pre-modern craftsmen extracted reliable practical value from a substance whose full elemental composition remained unknown to them. The long overland trade in borax from Tibet, a route significant enough to shape which parts of Europe had reliable access to a good metalworking flux at all, is a reminder that a compound's chemical simplicity says nothing about how difficult or costly it may have been to obtain in practice.