C-type asteroids, or carbonaceous asteroids, are a class of asteroids primarily composed of carbon-rich materials. They are the most common type of asteroid, making up about 75% of known asteroids in the Asteroid Belt. Their dark surfaces reflect very little light, which is why they appear black or very dark in color. These asteroids are believed to be some of the oldest objects in the solar system, dating back to its formation over 4.5 billion years ago. C-type asteroids may contain water and organic compounds, making them of great interest for studies related to the origins of life on Earth and the potential for future space exploration.