Stony iron meteorites, which are relatively rare, are composed of iron and silicates in about equal proportions. Most stone meteorites contain small, spherical particles, or chondrules, composed of the silicates olivine, pyroxene, or orthopyroxene. While chondrites may contain 50 different minerals along with nickel-iron, achondrites contain mainly pyroxene and plagioclase. Nickel-iron is only rarely found in achondrites. They have never been observed to fall.
Iron meteorites are the type most often found, because of their unusual appearance.
Stone meteorites are actually more numerous, but since they resemble ordinary rocks, they are not often found unless a fall is actually observed. A special class of chondrites of particular interest are the carbonaceous chondrites, which consist largely of the mineral serpentine and contain amino acids and other organic compounds believed to be of extraterrestrial origin. Meteorites have never been observed to fall during a meteor shower, which indicates that they are not remnants of comets. A very few meteorites have been identified as lunar in origin, but most are believed to originate from large parent bodies that formed at the time of the formation of the solar system and later broke up. Halley Taurids Oct.