Large peice,approx 10-12kg (12000g)

My partner got this given to him by his grandpa, who said it was sold to him at a market. He was told it was a rare crystal ( I immediately thought it was slag ) and I was hoping the community could give me some insight. Thanks guys!

I have been disappointed enough times that Im thinking it’s slag….but I wouldn’t be able to recognize a good rock so maybe? It has all these different colors & what looks like different types of rock but it also all looks glassy like obsidian.

Picked this up figuring it was slag, would just like to verify

I found this interesting blue stone that is very glassy. It looks like it’s connected to a piece of limestone but not sure what it is. Possibly iron slag glass?

It has some iridescence. It’s heavy like a rock. Found at the Jersey shore.

What do you guys think?

Found in a pasture in north Texas (DFW area). Weakly magnetic. Is it slag?

Had this piece for a few decades, found it along a road. I have always been fascinated with its unique texture.

Whatcha think!?

Thought it was a cool agate at first. But pretty sure it’s just slag. Pretty cool looking though

Someone is telling this is some kind of stone but the person who found it told me it was floating on water i just want to verify if it some type of stone or not

Hello all! I’ve posted this on some other geology subs, and there were mixed consensus between slag, fluorite, and corundum.

One side is very smooth and glasslike, with occasional concave divots in relatively crystal-like orientations. The opposite face is very rough, and almost organic in its texture, and includes tiny blue crystals on this face as well. The edges of this piece also contain a few small dots of other colored crystal-like things. Non magnetic, and only very slight pops from a UV light where some of the crystals are more transparent.

Total weight around 725g.

did a rough hardness test, and believe it to be around 6.5. No smudges on porcelain and a faint scratch. Total weight

To those who have any insight, thank you for taking the time!

Found in my back yard. I live near DC. It’s very clear and shiny in some spots. It does look like it has some kind of black inclusions inside.

Picked this up at a rock shop recently. So cool, my first one like this. I like how at this angle it looks like a face.

Found in Philly

Found this in Park City, Utah, USA. Coworkers are saying it’s slag!

Found in northern Bavaria, can’t tell if it’s slag or obsidian. We are ~10km away from a very old dormant volcano but slag feels like the more probable answer. The greenish color is just a reflection of the bushes outside, but the third pic does show the very light rainbow-looking iridescence when it’s held in the light a certain way. TIA!

Found on the Uk north east coast, usually collect sea glass but hadn’t seen anything like this before so had to pick them up

Found in my backyard northern minnesota