Most black pigments used both throughout history and currently are primarily carbonaceous. They most common carbonaceous pigments are graphite, charcoal, and soot. Some more exotic carbon-based pigments do exist, but are not commonly used.
The Miller lab has used Raman spectroscopy to determine the conjugation length of soots (see more here). Our lab has been using Raman non-invasively to examine black pigments commonly used by artists. Raman gives a number of parameters for the soot that we can record and use for principal component analysis to try and categorize the soots. We are specifically focused on different soots used to make the inksticks commonly used in East Asia. In a collaboration with the Freer|Sackler, we have tested our methods on a number of different inksticks.