ASTEROID
Asteroids are minor, rocky planetoids that usually inhabit a belt in the middle of a star system. They are the remnants from the star system's birth and represent the rocky material that did not form a terrestrial planet. They can range in size from a couple of centimeters to hundreds of kilometers across, and are generally rich in minerals. While some may be spherical and possess a tenuous atmosphere, most have an irregular shape and no atmosphere at all.
CLASS A: OLIVINE
These greenish asteroids are composed primarily of the mineral olivine. They are among the rarest type of asteroid in most star systems.
CLASS C: CHONDRITE
The most common variety of asteroid in any given star system is the chondrite. Composed primarily of clay and silicate rocks, they tend to be dark in appearance. They are also among the oldest objects in a star system.
CLASS M: METALLIC
Composed primarily of nickel and iron, these asteroids tend to vary based upon how close to a star they formed. In an asteroid that formed close enough to a star to become partially molten, the iron would have sunk to the center, forcing basaltic lava to the surface. Asteroids further away would remain a mixture of nickel and iron.
CLASS S: SILICATE
These stony asteroids are composed primarily of silicate materials and nickel-iron.