NOW, THAT IS A KNIFE! And, what is the spark test?
Take a piece of steel to a grinding wheel.
The more branches the sparks create(e.g they look sort of like a sparkler) the higher the carbon content. Alloys can also be detected... but thats pretty dang hard.
the darker orange the sparks the harder the steel in my experiance. I had a piece of chrome-vandanium-nickel alloy steel. Made it into a dagger-thing. It was shaped like a 20 inch katana blade. made a handle, put an edge sharp enough to shave. After 2 shaves and I don't know how many saplings its still razor sharp. and yes, i did shave with a dagger.