Gordran

But is it correct that the scanner does not even mention Graviolium?

I don't know. I tried scanning it with the stock surface scanner,but no Graviolium is shown there.

I do have problems finding Graviolium. I catched 2 asteroids into Kerbin orbit and started mining them, but after quite a while the graviolium tanks attached to the miner are still empty. Is there something wrong in the way i try to collect Graviolium or is it just bad luck?