Previously, when Cheng Ziang used a group of Kedal metal swords to chop stones, the stones were indeed chopped, but the sword body was severely damaged. It wasn't the Kedal metal that was damaged, but the sword handle, which became unusable. Otherwise, the hands of the one wielding the sword would be harmed by the backlash from the Kedal metal.
As mentioned before, Kedal metal is a type of metal that can handle soft but not hard treatment. If you force it hard, it can utterly disintegrate you, but if you go soft on it, it is at a loss. Thus, Elves have always mined Kedal metal in this manner, utilizing high temperatures to render it passive, then shaping it.
Generally speaking, once Kedal metal cools down, it regains its reactive nature, but Earth's scientists had treated these two swords such that all parts, except for the blades, are permanently rendered passive to ensure the safety of the users.
