Good evening! I've been a lurker for some time now but I found some steel at work today and can't seem to figure out what it is so I figured it was time to ask some experts. Thank you in advance to anyone who looks!

Looks like the tip of a brush hog blade to me.  Others?  The alloy would be what alloy *that* manufacturer used at *that* time...Spark testing would help narrow it down.

Throws off some bright sparks, short bursts. So I guess it's a mild steel?

Yes, No, Maybe; as we have no clue as to how you evaluate "Throws off some bright sparks, short bursts."

Sorry, I realized how bad of a description that is after I hit submit. I can snap a picture of the sparks from the grinder when I get to work tomorrow. If I had to go by memory and by the chart in "Metallurgy Made Simple" I would say they were "many fine repeating sprigs" so possibly manganese steel? I think?

Looks like a worn/broken cutting edge, the break is through runner bolt hole.  but . . . ?

Frosty The Lucky.

Coworker found it sitting on a rock while he was walking around picking up trash, very possible one of the landscapers hit one of the "ornamental" rocks around the driveway. Just seemed too big to be a mower blade, but I do agree it looks like it snapped at a bolt hole. Also: it's nice to meet you frosty and Thomas, I always look forward to your responses in threads and you've unknowingly helped me a lot in my short time (about 9 months) forging.

I have hit lots of rocks and various other hard objects mowing grass, trashed hundreds of blades and have never actually broken one, they all just bend, not saying impossible but I have never seen one break off in the past 16 years. 

Wear plate/blade for a bucket,grader,etc, my guess it is a hard face steel

Unknowingly helpful is a specialty of mine.

Frosty The Lucky.