Psyche is considered the tenth most massive main-belt asteroid and contains about 1 % of all the mass in the main-belt. Its mass has been estimated based on its gravitational effect on asteroids 94 Aurora and 13,206 Baer during close flybys. Over the last 10 years, the diameter has been estimated to range from 186 to 288 km, which makes the bulk density difficult to estimate, and everything from 1.8 to 7 g/cm3 has been published.
Psyche has a featureless spectrum and a surface reflecting 12 % in the visual light and an exceptionally 42 % in radar, making it a metallic-rich M-type and an Xk-type. If the density turns out to be close to the 7 g/cm3, then it points toward the composition of Psyche being almost pure iron-nickel. In that case Psyche would once have been part of the metallic core of a differentiated body, which experienced a catastrophic collision, leaving the core exposed. The high metallicity makes Psyche a promising site for planetary mining...