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Iron meteorites, also called siderites or ferrous meteorites, are a type of meteorite that consist overwhelmingly of an iron–nickel alloy known as meteoric iron that usually consists of two mineral phases: kamacite and taenite. Most iron meteorites originate from cores of planetesimals, [3] with the exception of the IIE iron meteorite group. [4]
Meteoric iron also has an effect on the Earth's atmosphere. When meteorites descend through the atmosphere, outer parts are ablated. Meteoric ablation is the source of many elements in the upper atmosphere. When meteoric iron is ablated, it forms a free iron atom that can react with ozone (O 3) to form FeO. This FeO may be the source of the ...
Stony-iron meteorites constitute the remaining 1%. They are a mixture of iron-nickel metal and silicate minerals. One type, called pallasites, is thought to have originated in the boundary zone above the core regions where iron meteorites originated. The other major type of stony-iron meteorites is the mesosiderites.
The Aletai meteorite, previously also known as the Armanty meteorite or Xinjiang meteorite, is one of the largest known iron meteorites, classified as a coarse octahedrite in chemical group IIIE-an. [b] In addition to many small fragments, at least five main fragments with a total mass over 74 tonnes have been recovered, the largest weighing about 28 tonnes.
The meteoric iron of stony-irons is similar to that of iron meteorites, consisting mostly of kamacite and taenite in different proportions. The silicates are dominated by olivine . Accessory minerals that also include non-silicates are: carlsbergite , chromite , cohenite , daubréelite , feldspar , graphite , ilmenite , merrillite , low-calcium ...
The Willamette Meteorite weighs about 34,200 pounds (15,500 kg). It is classified as a type III iron meteorite, being composed of over 91% iron and 7.62% nickel, with traces of cobalt and phosphorus. The approximate dimensions of the meteorite are 10 feet (3 m) tall by 6.5 feet (2 m) wide by 4.25 feet (1.3 m) deep.
Nonmagmatic meteorite (also nonmagmatic iron meteorite) is a deprecated term formerly used in meteoritics to describe iron meteorites that were originally thought to have not formed by igneous processes, to differentiate them from the magmatic meteorites, produced by the crystallization of a metal melt. [1]
The Muonionalusta meteorite, probably the oldest known meteorite (4.5653 ± 0.0001 billion years), [4] marks the first occurrence of stishovite in an iron meteorite. The mineral muonionalustaite, a hydrated nickel chloride, was first found as a weathering product from a meteorite sample.