Rather than silver, Cloi'yronai's Barrier is shot threw with a metal which does not oxidize and, thus, retains its silver color. This metal harms undead, much like cold iron harms devils. (Need to add this to all undead descriptions.) Metal is "timur".
Harder than adamantine, the smelting and working of timur is a closely guarded secret of the church of Cloi'yronai. (The church of Arsayos desperately wishes to steal the process.)
Mining of timur from the Barrier is banned, but the church does permit the harvesting of the ore from naturally fallen boulders and scree. The metal thus gathered is used to create weapons and armor to be giyen as awards to those who have valiantly served the church. (The frequency of such awards is equivalent to that of our Congressional Medal of Honor.)