Schimmel bridge graphite

[John D. Chapman]

Last week I tuned a Schimmel 6' grand, 25 years old.  It was in good
shape and tuned well.  However, the entire area of the bridge which
normally has black graphite was covered with gray powder and very thin
gray peelings which could be blown away by the slightest breath.  The
strings were not rusted or corroded, but what is that stuff?
John Chapman RPT
Wake Forest University
Winston-Salem NC