C-type asteroids are
carbonaceous asteroids. They are the most common variety, forming around 75% of known
asteroids, and an even higher percentage in the outer part of the
asteroid belt beyond 2.7
AU, which is dominated by this asteroid type. The proportion of C-types may actually be greater than this, because C-types are much darker than most other asteroid types except
D-types and others common only at the extreme outer edge of the
asteroid belt.