True, rocks are made from hardened magma from the Earth’s interior. By studying them you can find out a lot about the interior.
I had a carved lava rock necklace when I was a kid & lived in Hawaii. My sister & I developed a rash from wearing the lava rock pendant. We think it was because there was a high level of sulfur in the lava rock.
If you have ever been near an active volcano, the smoke/ steam gives off a smell of sulfur, which smells like rotten