Thanks Jim and Peter for your replies.
I think now that there’s something other than copper/silver in with
the gold in this ‘21k’ bracelet.
I’ve done a bit of an assessment of the parts of this bracelet and
notice these points. The catch is made from rectangular bar, is
stamped 21k, and curiously is also the more malleable component where
the metal colour is similar to 22ky. The very thin ‘coin’ parts which
seem to be mechanicly stamped are of a very hard alloy, and are so
hard it’s at the cost of malleability. Torch heating produced a very
blue/ultramarine colour at first. When ‘annealed’ there was little
difference in bendability, and cracked when bent almost in half.
Post-anneal quenched in water the metal is a deep blue-black.
A small ingot (poured Satsuo Ando method into water) produced a
cleanish button with a single large bubble in the top. Sawed in half
and rolled it made a very tough 0.5mm piece of sheet metal with some
(but not bad) edge deterioration. With the other half of the button I
rolled out a reasonable piece of 1.8mm square rod. But again it’s
nothing like as malleable as any other 22kr I make.
It’s only useable for ring shanks, bezel bearer and such jobs.
Has anyone else experienced this kind of metal?