What kind of lightweight block is this?

I recently bought a house and until now I assumed that the walls were made of Poroton. However, I no longer believe that. Can someone identify this lightweight building block?

It seems to be a material mix with integrated insulating materials. Something with expanded clay?

Please help.

Looks like pumice to me.

I want to try to find out something about the insulation value. How do I go about it if I don’t exactly know what I am dealing with? If it is pumice - what are the black inclusions then? A mix to improve the insulation?

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

This is not pumice, this is in my opinion dyed expanded clay; there is nothing filled in.

Rhenish greetings