C-type asteroid
The largest unequivocally C-type asteroid is 10 Hygiea, although the SMASS classification places the largest asteroid, 1 Ceres, here as well, because that scheme lacks a G-type.
Standard asteroid physical characteristics
Such estimates can be indicated as approximate by use of a tilde "~". Besides these "guesstimates", masses can be obtained for the larger asteroids by solving for the perturbations they cause in each other's orbits, or when the asteroid has an orbiting companion of known orbital radius. The masses of the largest asterois 1 Ceres, 2 Pallas, and 4 Vesta can also be obtained from perturbations of Mars.
While these perturbations are tiny, they can be accurately measured from radar ranging data from the Earth to spacecraft on the surface of Mars, such as the Viking landers.