Henry Kolesnik wrote:

A sharp pocket knife or a triangle file doesn't mark it...
Whatever it is, it's quite hard...
The melted blue resistor which I assume is what it is looks like it was
replace in the past..
The circuit board is toasted all the way thru and backside is nearly black.
I've never seen a glass, ceramic or whatever melt like that, has anyone
else?

Oh yes!
Melted the glazing on a 2KW wirewound resistor (nice glowing RED).
Value changed slightly.
In this case, if the wires did not shift to make for one-turn short,
that WW resistor should measure at lest in the ballpark of what its
value originally was.