The surface is covered with a layer of germanium oxide which is
why it doesn't firescale.
Some more detail on this. OK at my age I am a bit Led Zepplined aka
Dazed and Confused with specs. But I believe that when Argentium is
heated the Germanium "eats" the oxygen before the oxygen can get to
the copper and make firescale.
But whatever the tech specs Argentium does not produce firescale. I
have found it works like sterling but solders like 18 Kt yellow.
Argentium is the most wonderful silver of all and Peter Johns will
go down in history for his invention. I praise him every bench day.
What I like most about Argentium is stamping it with the flying
unicorn. About which the wife and daughter think I am an idiot.
My son does not because I will stop making him Argentium guitar
picks if he does.
all the best