Help to ID a rock

Help to ID a rock

Flaky, soft-ish (marks a paper like a graphite).
See picture.


Slate from various quarries one being in fish hatchery and off of Morgan's field.

How heavy is it, and where was it found?

It actually looks more like charcoal to me, than a rock. Shale normally won't write on paper, at least the shale I've seen, even oil shale. Slate is nomally even harder than most shale, and even less likely to "write" on paper.

I'm guessing it was part of a log or branch that was in a campfire and burned, but smothered, burning without extra oxygen from air exposure, turning all the wood into charcoal. The "layers" look to have something of an arc to them, and don't seem straight, as most bedding planes would be.

Take a layer off of it, and somewhere safe, try to light it with a match or a lighter. It could be tree or plant matter not completely metamorphosed into actual coal, which would make it "lignite", or brown coal

My only other "rock" guess would be a micaceous schist, with a heavy amount of graphite in it. I don't know of any deposits of that in the area. I've seen graphite more up in Sussex County around the Limecrest Quarry, but not sure of any deposits close by.

So, my final answer, lignite (google it), or charcoal.

Phil D. Phil D.
March 14th

Phil, did you say schist? Don't be obsidian.

March 14th


I try to play gneiss...until it's time to not be gneiss, then I go all flinty and sometimes schisty for good measure.

Phil D. Phil D.
March 14th

not quite shale...unless there are varieties I didn't see in a book.
too flaky for slate. Slate is more dense.
Regarding its weight - it's definitely heavier than a charcoal, but lighter than onyx.
Phil D. - igniting?! That sounds nice. Not gneiss....
It was found near Allamuchy (there's a park on 517 north of highway 80).

I already took that for granite.........

March 15th


Did you check a bit to see if it would light? Since you don't think it's charcoal, though a naturally heavy wood would still likely make a heavyish charcoal, not like the commercial varieties. Curious to see it in person. The picture does look like either lignite or charcoal, moreso than anything else I've seen. I don't know if Gary M. reads this forum, but as a mineral collector and dealer, he may know. Was there more of it in that area, or just this one piece?

Phil D. Phil D.
March 15th

Phil D,
I didn't "play" with it, yet. That was the only "rock" in the immediate area, but, honestly, I didn't search for more specimens of this "rock".
Will post later after I "ignite the sky".

Re: Help to ID a rock

Exposure to flame (natural gas) didn't ignite it. The fridge got orange and turned to lighter gray.
This rock doesn't pass electricity, either.
Unexposed to air layers are slightly darker (gray).

From this angle, it looks like gray shale, but I'm no geologist.

From this angle, as opposed to the other view, it looks more like a shale. Definitely agreeing with Ian here, especially since it doesn't light. Lignite, or other softer coal, would have, or at least, should have, ignited.

OK. Thanks for your inputs. Shale!

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