Strange Rock Found While Metal Detecting

[The Pest]

Howdy Sirs... While goofing around this afternoon... I was telling a buddy of mine about this rock... And what I was learning here on the forum... He said he worked with a geologist... so we sent the guy a picture... And the guy wanted to see the rock... so we took the rock to the geologist guy... he had a box of rocks... I think it's one of kits the members here were describing (pictured)... There was also several magnifying glasses and what looked like dental picks... He scraped each one of the rocks from the box across mine and determined it was between  8 and  9...  He poked and prodded and examined it intently... At one point he said he thought he was seeing some gold... It's too hard to be Arsenopyrite... But he's 75 percent sure it's Chromite Ore... Then he said Not To Lick It (why would I lick it)...  If I am understanding what he was describing correctly... I should not lick any ores because arsenic is present when ores form( I am Not Going to Lick Rocks)...  I am defiantly having fun learning about this... All these years I've been diggin rocks and dirt lookin for stuff (mostly aluminum)... And never considered the geology at all.... It puts a whole other spin on metal detecting... what else is there after I retrieve my target....

[Againstmywill]

My thought.

[Geologyhound]

Againstmywill is on to something here.  Ferromanganese is not magnetic (Ferrochrome is magnetic).  Ferromanganese typically has a dark crust which your pictures show (Ferrochrome does not).  The high density fits.

I cannot find any hardness information online.  That may be because of the wide range of possible compositions in the Fe-Mn series along with other elements/minerals which may be added at a foundry to achieve specific properties.

[Againstmywill]

I'm guessing you found it in close(ish) proximity to railroad tracks?

[The Pest]

Howdy Sirs.... Wow.... It's Amazing how the flood gates can open... Ferro Manganese - an indispensable deoxidizer and desulpherizer in the Steel making Industry... This stuff has been.. and is..  heavily traded globally... Two other names I found referring to it are Ferro Chrome and Silico Manganese... so I'm guessing there are different grades of this stuff... Lots of pictures... I added a few I found... Many look exactly like my little rock... My 11 year old mystery appears to be solved... And I've learned quite a bit about some thing so simple... I can't thank everyone here enough... ( I am still Not going to lick it )

   As to where I found the little rock... I dug this up in a wooded area that used to be a farm field in the early 70's  next to Hwy Rt. 40 in South Jersey... It was a great place to poke around... the farm house had burned down decades ago... The remnants of the outhouse was still there(no I did not dig it up)...The farmers dump was way in the back of the property encrusted in sticker bushes... I found all kinds of cool stuff around the property that summer(mostly aluminum).... but the Rock was up near the road in the edge of the woods... where the field would have been years ago... It may have simply fallen out of a truck... and got plowed around for me to find 30 some years later... small world

 

[Clay Diggins]

So it's neither a rock nor a mineral. It's a man made commercial product. Made in a blast furnace used for processing iron. New Jersey had a lot of production of iron manganese ores in the Piedmont region.  Probably did fall off a truck, it's not like it would be used in farming. 😀

[jasong]

Nice call @Againstmywill That looks like a likely ID. I learned about a new manmade material too.