How do stony-iron meteorites differ from stony and iron meteorites?

Meteorites are traditionally categorized into three groups—stony meteorites, iron meteorites, and stony-iron meteorites—based on the proportions of silicate minerals and nickel-iron metal they contain.1

Stony-iron meteorites serve as an intermediate type, containing substantial and roughly equal amounts of both rocky material and nickel-iron metal. In contrast, stony meteorites are composed primarily of silicate minerals, while iron meteorites consist almost entirely of nickel-iron metal.21

These categories often reflect the process of geochemical differentiation within parent bodies like asteroids. If an asteroid melts, dense metallic components sink to form a core, while less-dense silicates form a mantle. Stony-iron meteorites, such as pallasites, are thought to originate from the interface between these core and mantle regions. Other stony-irons, known as mesosiderites, are impact breccias that contain a large amount of dispersed metal, likely resulting from collisions between different planetary bodies.132