Um… Rock ID? 😆

[Matth05]

Could possibly be my weirdest MFK post lol. Spotted an interesting rock while fishing today, buried in the sand on the bank of the river. Decided to take it home and clean it up, but I can’t figure out what the dang thing is. I originally was thinking some sort of obsidian, but I’m most likely way off. Google Lens wasn’t very helpful either (which seems to be the case most of the time), and was giving a ton of different answers depending on the angle of the photo.
Whatever it is, it’s most likely being put on the shelf in my room with my other random collectibles .

 

[danotaylor]

Very cool looking piece for sure. I'm for sure no geologist, basalt maybe??

 

[Sassafras]

No expertise here either, but I can see why your first instinct was obsidian. It has the smooth, glassy fracture chips like you would expect from obsidian or a flint-type rock. Is the brown a stain or dirt on the surface or is it also rock of a different color?

 

[Matth05]

No expertise here either, but I can see why your first instinct was obsidian. It has the smooth, glassy fracture chips like you would expect from obsidian or a flint-type rock. Is the brown a stain or dirt on the surface or is it also rock of a different color?

Definitely not dirt. My guess was iron spots? Maybe oxidation? It flakes off pretty easily with my fingernail, exposing more shiny black underneath. Don’t want to mess with it too much. The rock itself is quite brittle, I’ve already accidentally flaked off very small pieces trying to get the brown spots off.

The more I look at it under bright light, I’m seeing that in some spots there’s almost a blue/green iridescence.

 

[jjohnwm]

I've seen similar before. I can absolutely confirm your instincts are correct: it's a rock.

 

[SilverArowanaBoi]

I'd argue one of these: Hematite or Black Tourmaline

It look more like raw Hematite, here are some pictures for reference:



I'd also argue Hematite because you mentioned that it was brittle and hematite has a Mohs Hardness Scale of 1-6 (1 is very soft, and 6 is moderately hard). Black Tourmaline is around 7-7.5 on the Mohs Hardness Scale so it wouldn't break easily. But here are some pics of black tourmaline for reference:



Either way, its a beautiful specimen, defintely keep it!

 

[SilverArowanaBoi]

It's not Obsidian because Obsidian has a more "wavy" and glassy texture in its raw form vs. bumpy and veiny. Here is a picture for reference:

 

[SilverArowanaBoi]

Oh, and one sure way to test if it is hematite is to scratch it on a tile or some hard surface like concrete, and it will leave a brown-to-red residue.

Something like this:



Sorry if its a lot of info, I'm also very passionate about rocks lol

 

[SilverArowanaBoi]

Definitely not dirt. My guess was iron spots? Maybe oxidation? It flakes off pretty easily with my fingernail, exposing more shiny black underneath. Don’t want to mess with it too much. The rock itself is quite brittle, I’ve already accidentally flaked off very small pieces trying to get the brown spots off.

The more I look at it under bright light, I’m seeing that in some spots there’s almost a blue/green iridescence.

There are definitely signs of hematite; it scratches off easily with a fingernail.

 

[Matth05]

Interesting, hematite was in the pool of different answers google was giving me. When scratching on both concrete and tile it’s actually leaving a black residue? It’s earned a spot on my shelf regardless lol.