🔎 UNIDENTIFIED It's extremely hard, broke all my tools. Light shines through and the parts that are fractured it extremely bright in the sun.

[SunnyYou]

 

[schreib69]

I have tried a magnet?
Does it appear molten / refrozen? possibly meteoric?
Almost everyone owns a grinder. I'll bet my grinder will go through it. Different blades available including diamond blades($40). I have used them for cutting block for retaining walls.
Please report in your results after using a grinder.

 

[tamrock]

So you destroyed the 12 lb sledgehammer.
It doesn't show impact marks.

Maybe these are his tools. I'll bet I could turn that piece of common granite into dust with an 8lb sledgehammer.

 

[Zakon Krzyżacki]

Looks like regular old decaying granite.
Common in my area.
I am blessed to live near the center of the Michigan basin.
All the heavy stuff got dropped by the glaciers here.

 

[unclemac]

there is no doubt that is an intrusive igneous rock...have a look

Google Search