I tried to look for any similar rocks on the Internet but couldn't find anything and I don't know much about geology.
I've been given this rock when I was a child and now I'm just curious to know what it is.
To me it looks like a rock around a rock, I don't know maybe lava of some sort ended up around a regular rock and that's the result.
If you could enlight me id really appreciate
Regarding its properties
The inside rock (from now on that's how I'll call the white part inside) is white, milky and not transparent.
The outside rock (the black part around) is grey, almost a metallic color. The border are darker almost black you see it clearly on the second picture.
You can see my hand as a scale it is approximately 6/7 cm long and 2/3cm thick.
Weight is normal to me but again I'm not a specialist.
I have no idea where it was found, the only info its original owner gave me was that he called it an "enrobé" (I'm French and that's a French word which means that something is around another thing)
Regarding its hardness, I don't want to break it but my fingernail definitely not scratch it.
It doesn't smell anything.
Also there is a brown stain (see picture 2) but I don't know if it's natural or not. It looks like it has nothing to do here.