I have heard of a spark test. I know that I have a bar of 4340 steel, but I
have "lost" it. I can't tell it for sure from some other stock that I have
around. I have one bar that is still clean and bright despite the high
humidity and condensation in the shop these days so I think that may be it,
but I have heard of a spark test - basically, the sparks from grinding are
different between different steels. Anything?

thanks, Brian