Name that rock or at least help me identify one

The kiddo is supposed to bring in rocks tomorrow for a class project.  I was digging through some that we have collected over the years and found this one.  I remember picking it up along some railroad tracks in Houston.  I remember asking the RR crew nearby what it was and they told me but that was 10+ years ago.  I know its not silver or anything valuable as I would remember and they wouldnt have left these scattered along the tracks.   If it matters, it seems light for its size, but I don't have a scale to weigh it.   It isnt magnetic.  I didnt polish it, so this is how I picked it up off the ground.  

Any ideas? 

Hard to tell, maybe iron pyrite?

Edit - below are some iron pyrite samples being sold from China.

FieroReinke said:

The kiddo is supposed to bring in rocks tomorrow for a class project.  I was digging through some that we have collected over the years and found this one.  I remember picking it up along some railroad tracks in Houston.  I remember asking the RR crew nearby what it was and they told me but that was 10+ years ago.  I know its not silver or anything valuable as I would remember and they wouldnt have left these scattered along the tracks.   If it matters, it seems light for its size, but I don't have a scale to weigh it.   It isnt magnetic.  I didnt polish it, so this is how I picked it up off the ground.  

Any ideas? 

 

 

That sure looks like a Frederock to me, it's far too small to be a Billder. 

In reply to FieroReinke :

I don't think that's a rock. It looks a lot more like the cooled molten slag from my grandfather's chrome shop than it does anything igneous or metamorphic. I'd go with aluminum or vanadium given the reflectivity.

Space peanut?

Not a rock lobster.

Looks like the stuff I skim off the top of an aluminum melt in a crucible.

I used to find galena along the tracks where I lived, and was told it was part of the fill used when laying down the tracks.

The sticker is that what you have seems porous, and galena isn't. Could it just be a piece of slag?

Javelin said:

In reply to FieroReinke :

I don't think that's a rock. It looks a lot more like the cooled molten slag from my grandfather's chrome shop than it does anything igneous or metamorphic. I'd go with aluminum or vanadium given the reflectivity.

 I was thinking it looked like some kind of metal slag, and aluminum was my top candidate.

I don't think its aluminum slag.  I think I would remember the RR crew telling me it was aluminum slag.  

I am not sure on the iron pyrite, it does't have any yellow coloring.  It is all silver in color, and very consistent in color.  

It would be funny if it was Galena, as it was actually found on RR tracks in Galena Park near the ship channel in Houston.  

I have been looking online and I think its silicon metal.  This sounds right from what I remember the RR crew saying.  

https://www.sialloy.com/products/silicon-metal.html

Looking at the patterns in it I still lean toward aluminum dross. If it was being moved around in quantity and shipped somewhere it would get smoothed out like your sample, like a river rock does. The silicon metal is used a lot with aluminum to make better alloys so there may be some in there.

Put a few drops of muriatic acid on it, see if it gives off hydrogen.

could be Zinc  https://geology.com/usgs/uses-of-zinc/