P-type (primitive-type) asteroids have low albedo and a featureless reddish spectrum.
[2][3] An early system of asteroid taxonomy was established in 1975 from the doctoral thesis work of David J. Tholen.
[4] The P-type asteroids are some of the darkest objects in the Solar System with very low albedos (pv<0.1) and appear to be organic-rich, similar to carbonaceous chondrites.
[5][6] The reflectance spectra of P-type asteroids can be reproduced through a combination of 31% CI and 49% CM groups of carbonaceous chondrite meteorites, plus 20% Tagish lake meteorites, after undergoing thermal metamorphism and space weathering.
Both Sylvia and Camilla have moons and indications that they have been be disrupted, but they are also quite massive, at over ×1019 kg, and so are unlikely to have much internal porosity affecting their densities.