My two sons and I were almost literally digging shit up today when my youngest son found this rock. I know what it looks like to me, but we are in Northern Michigan and there isn’t supposed to be any of it here. It came from the fill dirt over our septic tank. I’m almost positive the fill dirt was local. We’re closer to Canada than we are to Ohio or Wisconsin.

If it is indeed a rock my guess would be a piece of petrified wood..

I'm going to second smlsig and say petrified wood as well.

Agate

I can tell you it is not a diamond.

I'd call that flint

The ridges on the outside almost makes me believe it's a fossil of some kind.

Chert or flint nodule with limestone.

Could be obsidian from the color (black). Looks like concentric fracture. Its not gold. Could also be the product of some sort of heat, like in smelting operations. Like volcanic glass. Been too many years and too much beer for me to remember.

I'd second the obsidian and it looks like it was shaped by being in water, like a rock on the seashore.
How close are you to the great lakes?

Another example.
https://www.proxibid.com/2-1-2...information/56441884

Obsidian by the way it breaks, but that’s just my educated guess.

Isn’t Obsidian more glassy/shiny?

quote:

Originally posted by 220-9er:

How close are you to the great lakes?

120 feet give or take. Last year the lake level was way up and almost lost that tree.



Flint looks like good guess. The black strips don’t seem to be translucent like obsidian. Petrified wood was my first guess, but I don’t think it’s possible in Michigan. We find a lot of coral fossils on the other hand.

I am no expert, but obsidian can have bands.

The ones pictured are very convoluted, but that could have been due to movements of the material as it cooled.

Agates are common on the shores of Lake Superior. Lots of folks hunt and collect them. Thats my guess, anyway.

I haven't been into my amateur rock collector phase for since the mid-60s. My guess is a form of petrified wood.

It's a piece of Chernobyl.

Meteor.

quote:

Originally posted by sigmonkey:
Meteor.

That's a big ol' piece of poopie!

My guess is Obsidian, I've collected some that looks like that. Here's a picture of some, I wet it to show better. Obsidian was important to Native Americans and moved all over the country from deposits in the West. Mine was collected in an area where there was an Indian quarry for Obsidian.

It’s waxy and not at all glassy like obsidian, plus it scratches glass so it is harder than obsidian. Volcanic activity in Michigan ended over a billion years ago when the Midcontinent Rift failed. The Michigan Basin was then formed and the Lower Peninsula was subsequently buried under multiple layers of sedimentary rock. Interestingly enough, our little spot in Presque Isle County is part of the Detroit River Group. That all happened hundreds of millions of years ago and what covers that now is glacial drift from when the Wisconsin invasion receded about 35,000 years ago.

The fill dirt around our septic tank is consistent with glacial drift which includes chert and flint. My son’s sample looks just like pictures we’ve found on the internet of what’s called banded flint.

SIGforum comes through again with a correct response in 15 minutes. Thanks for all of the responses. My son and I enjoyed researching them all and figuring out what he has and learning things we wouldn’t have otherwise.