Making black stems

Hi All, I am in the process of planning a piece (earrings? brooch?)
based loosely on a type of fern that has jet black, shiny stems. I
want the stems to appear that way but the only silver blackener I’ve
used is along the line of Jax on sterling silver which does not give
the luster (quality?) I’m looking for. I am planning on making the
leaf blades in sterling but is there another material or treatment
that might give a nicer result for the stems? Thanks very much in
advance. Richard

If you can find it, black coral is just the thing. The best polishes
up to a beautiful luster. You must be careful not to overheat it
during polish or it will turn brown. Some specimens have a golden
brown undertone. I have found small (diameter) piece on the beach in
S. Florida.