CHONDRITES
Ordinary Chondritic meteorites the most common of stony meteorites represent about 85% of the observed falls. Other chondrites are carbonaceous (C) enstatite (E) and a new group R-chondrites.Chondrites derive their names from the small spherical inclusions or chondrules they contain. How chondrules are formed is still being debated and they are comprised of olivines and pyroxenes. Chondrules can be prolific or hardly present and this helps to categorize them. |
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ACHRONDITES
The remaining 15% of all meteorites are either achondrites stony-irons or irons. Scientists believe that some of these meteorites originated on the surface of the Moon or Mars. 7.8 percent of meteorite falls are achondrites. These were formed by recrystallization either within or on chondritic planetary bodies. Achondrites are divided into two broad groups calcium-rich and calcium-poor.
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IRON
Iron meteorites seem to be from the core areas of planetary bodies. They are categorized as Hexahedrites (H) Octahedrites (O) or Ataxites (D) based on the structures found within them. Many have wonderful "Widmanstaetten" figures when they are sliced polished and etched. |
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STONY-IRON
These meteorites are mixtures of iron-nickel alloy and non-metallic mineral matter. Scientists believe that they are like the material that would be found where the Earth's core meets the mantle. 1.2 percent of meteorite falls are stony irons. These are mixtures of iron and stony material like type S asteroids. |
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