Asteroid Spectral  -  Type M

Type M, or metallic are mostly made up of nickel and iron including platinum group metals. Type M asteroids can also contain precious metals including gold, platinum and copper. 

The largest Type M asteroid observed from Earth is 16 Psyche, which is approximately 200km in diameter and located in the main asteroid belt and is historically believed to be comprised mostly of metallic iron and nickel similar to Earth’s core.