Stony-iron meteorites contain approximately even amounts of silicates and nickel-iron alloy, and are divided into two distinct groups: Pallasites and mesosiderites.
Pallasites are believed to form between the silicate mantle, or outer shell, and molten metal core of a differentiated asteroid. The primary silicate mineral in pallasites is olivine, distinguishable by its greenish hue.
Mesosiderites are brecciated stony-iron meteorites that contain nearly equal amounts of metal and silicates. They are likely formed by collisions of metal-rich and silicate-rich asteroids, and their silicate portion is composed mainly of igneous rock fragments. Fewer than 150 mesosiderites have been identified to date.
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