Need some help with an unusual rock

[Always L00kin]

I found this rock some 30 years ago in my parent's dirt floor basement. It is in the anthracite region of PA. I have taken it to a number of people and no one has been able to truly tell me what it is. the rock appears to be slate in color with a very thin coating that has a metallic appearance. It is non magnetic and does not rust or tarnish so it may not be metallic. I have never seen another rock like it so it seems to be unusual. I have attached some photos. So if anyone has seen something like this please let me know. I have considered it might be petrified wood with a metallic looking mineralization. I have considered that it might be slag of some sort but it is pretty uniform and rock like. I have also considered the idea that it may be some kind of stony meteorite. I really don't know. Take a look and see what you think.

 

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[Plug N Play]

Looks like anthracite coal.
Does it burn ?

 

[Always L00kin]

I haven't tried to burn it but I may. I have seen tons and tons of anthracite growing up in North East Pa. I do not believe its that. A local geologist here also agreed that is wasn't anthracite but could not tell me what it was.

 

[Reanm8er]

The specific gravity might be a clue. Weight per unit of volume. I think coal would be pretty light.

 

[Charlie P. (NY)]

http://www.treasurenet.com/forums/rocks-gems/168134-what-these-shiny-black-rocks.html

Slag (with bubbles).

 

[Geochem]

It does not look nature produced. That probably has thrown many in trying to ID.

It should feel heavy in your hand, like a peice of steel.

If it does feel heavy like its pure metallic, then it is a very unusual piece of slag, with probably copper as the primary component that gives it that penny-ish color, but has compounded with another element or two to result in its super bright shine and resistance to oxidation (i.e. any thin layer locations having different composition and lack of brilliance shine).

 

[Nitric]

I wonder if they would have thrown these in the coal furnaces to help hold heat?

My grandfather also talked about some type of "rock" they would heat up and put in their beds at night since the furnace was in the basement and some of the bedrooms in the house got cold by morning in further parts of the house.

I've seen something similar before and can't quite put my finger on it since my memory SUCKS!!!

No clue at the moment, I'm just throwing off the wall guess's.