Shungite

Shungite is a carbon-rich rock found almost exclusively in the Shunga region of Karelia, Russia. It's approximately 2 billion years old - Precambrian - making it one of the oldest carbon-bearing rocks on Earth. The exact origin of its carbon is debated: it may derive from ancient microbial mats (colonial organisms that predated complex life) or from migrated hydrocarbons.

What makes shungite scientifically notable is its content of fullerenes - hollow, cage-like carbon molecules (including C60, known as 'buckyballs'). Shungite is one of the only known natural sources of fullerenes, which were first synthesized in a laboratory in 1985 and earned their discoverers a Nobel Prize. However, the fullerene content is very small (typically less than 0.1% by weight), and whether this has any practical significance outside a laboratory is questionable.

Shungite is classified into types based on carbon content. 'Elite' or 'noble' shungite (Type I) contains 90-98% carbon and has a distinctive semi-metallic, silvery-black appearance. Regular shungite (Type III) contains 30-50% carbon and is matte black. The vast majority of shungite on the market is Type III.

Shungite is identified by its black color, low density (it feels lighter than most black minerals), and ability to conduct electricity (one of the few non-metallic rocks that does). The conductivity test is the most practical - real shungite will complete a circuit with a simple multimeter or battery-and-LED setup.

Distinguish from black tourmaline (striated crystals, doesn't conduct electricity), obsidian (glassy, much denser), jet (organic, very lightweight), and black onyx (banded, harder). Elite shungite has a distinctive semi-metallic, conchoidal fracture surface that's unlike any other black mineral.