These types may originate on the asteroid Vesta. Chassignites, Shergottites, and Nakhlites are grouped as SNC meteorites. These types are believed to originate on Mars. See H. McSween, Meteorites and Their Parent Planets for and excellent explanation. These meteorites are made of a crystalline iron-nickel alloy .
Scientists believe that they resemble the outer core of the Earth.
4.8 percent of meteorite falls are irons. Contains both kamacite and taenite and has Widmanstatten pattern. A second scheme for classifying iron meteorites is by their chemistry. The determining factors are groupings of meteorites with similar ratios of trace elements to nickel. Generally, the higher the Roman numeral of the classification, the lower the concentration of trace elements.