What is this Coal like object?

I picked this up today and I'm trying to figure out what it's made of and what it's intended use was suppose to be. I wasn't sure which forum to post this in so I hope it's ok here.

I think it's made of coal and it's polished on one side. It's about 7" in length, 3" in width and about 2" in depth and weighs about 1 pound 12 ounces.

Does anyone know what it was made to be and if it's coal? When I scratch it on rough porcelain it scratches black although it does not blacken my hands.

Thanks!
Kevin

 

I'd guess obsidian.

 

It doesn't look like obsidian,no visible conchoidal fractures. Just a wild guess , possible anthracite coal.

 

Argillite would hold that polish but it looks to be too porous to be a shale...

 

Could it be a gold test stone?

 

Is the polished portion definitely part of the original stone or is it a glued-on plate of black plastic or whatever? See if u can insert a sharp tool under a corner of it to check. Looks like an applied plate to me.

 

I'm wondering if it could be Lava Rock like this:

http://www.phillipscollection.com/product/sku/ph66050

 

Except.....that is resin.

 

I thought lava at first but I don't think it can be polished like this since it's so porous and I also think it would be lighter in weight.

 

Looks like it was going to be a commemorative piece of coal that nobody got around to putting the inscription on........maybe too soft for an inscription???

 

Searching "coal paperweight" and "coal souvenir" brings up some interesting things on Google Images, like this:

http://www.phoenixmasonry.org/masonicmuseum/yr_coal_paperweight.htm

 

Now, THAT'S cool!!!

 

Wow, now I'm more confused on what it's made of. Nevertheless, thanks for the replies! It is definitely not obsidian or volcanic glass like substance and it's not a volcanic rock. It's more like coal and scratches black on a piece of rough or mat finish white porcelain and does not chip when scratched on the porcelain. Could have been intended as paperweight or a commemorative piece or a display piece for that purpose. The surface has definitely been polished and is part of the original stone and has not been applied to the surface.

 

Could be a blank piece sold for finishing with an engraving, but for some reason it never got engraved.

 

Aquitaine... a follow up on your idea... anthracite.

https://www.google.com/search?q=yor...UIBygC#tbm=isch&q=anthracite+coal+paperweight

 

Nice!!

 

It’s coal. Coal polishes beautifully. It would be for engraving something onto. Beautifully piece of Anthracite.

 

Smithsonian..


2 bad Kevin hasn't been here since 2018..

 

It is called Jet

Jet is a black organic rock that forms when pieces of woody material are buried in sediment and are coalified. Though very similar to coal, it is less friable. Jet can be cut, carved, and polished to a bright luster. People have used jet for thousands of years to produce gemstones, beads, and many other objects