Glad you weren't hurt. Magnesium can be hazardous to your health.

Magnesium is amazing stuff. During WW II aircraft engine cases and
accessory plates were made of the stuff. If you had and engine fire in
flight you could not pout it out. It would burn through the wing spar
and  you lost the wing then the airplane. Happened lots in combat.
Magnesium burns with such intensity that it will burn in a pure CO2
atmosphere so a CO2 fire extinguisher will not put out the fire. It
separates the Oxygen from the Carbon dioxide to burn, and leaves behind
a heavy carbon soot.It is so active it will burn under water by
separating the O2 atom from the water molecule leaving only the Hydrogen
to burn of bubble to the surface.

Interesting stuff - magnesium

John
On 10/25/2013 4:42 PM, Jim Felder wrote:
> This happened last weekend.
>
> I was making a mount that would allow me to put an old Evinrude engine on a
> canoe. I grabbed a piece of angle that has been lying around my shop for
> about thirty years, used as a prybar, etc. I had always assumed that it was
> aluminum.
>
> I sawed it into the shape I wanted and then finished the edges with a
> grinder. After I dressed it out like I wanted it, I started in on my next
> project, a skid plate to go under my propane tank. As soon as I started in
> on the steel, the whole workbench lit up in an intense glow for a few
> seconds. I managed to get away without having holes burned in my shoes or
> setting the workbench on fire.
>
> Be careful when working with magnesium and then working with steel! This is
> one case where it really pays to clean up early.
>
> Jim
>