ᐅ What kind of lightweight masonry block is this?

I recently bought a house and had assumed that the walls were made of Poroton blocks. However, I no longer believe that to be the case. Can anyone identify this lightweight building block?

It appears to be a composite material with integrated insulation. Possibly something with expanded clay?

Looking forward to your help.

That looks like pumice to me.

I would like to try to find out more about the insulation value. How should I proceed if I am not exactly sure what material I am dealing with?
If it is pumice, what are the black inclusions? A mixture to improve the insulation?

I would say this is a lightweight concrete block. The dark part is the porous aggregate, which makes it a lightweight concrete block.

That is not pumice; in my opinion, it is colored expanded clay aggregate. There is no filler in it.

Regards, Bauexperte