Inorganic substance that is (1) naturally occurring (but does not have a biologic or man-made origin) and formed by physical (not biological) forces with a (2) defined chemical composition of limited variation, has a (3) distinctive set of of physical properties including being a solid, and has a (4) homogeneous that forms through processes such as weathering, and in the case of meteorites can also include pre-terrestrial alteration.
Secondary minerals in meteorites that formed during terrestrial weathering include oxides and hydroxides formed directly from metallic Fe-Ni by Oxidation and reduction together are called redox (reduction and oxidation) and generally characterized by the transfer of electrons between chemical species, like molecules, atoms or ions, where one species undergoes oxidation, a loss of electrons, while another species undergoes reduction, a gain of electrons. This transfer of electrons between reactants, phosphates formed by the alteration of Ni-Fe phosphide mineral, (Fe,Ni)3P, yellowish in color and predominantly found in iron and stony-iron meteorites. Schreibersite can also be found in a variety of other meteorites including some acapulcoites, aubrites, enstatite chondrites and achondrites, lunars, ureilites, winonaites and a smattering of other meteorite types like CM, CO and CB. Schreibersite, and sulfates formed by alteration of Brass colored non-magnetic mineral of iron sulfide, FeS, found in a variety of meteorites.. For example, surveys of iron meteorites have revealed that secondary minerals that formed by terrestrial weathering include1:
- Oxides and hydroxides formed directly from metallic Fe-Ni by oxidation and the incorporation of H2O, CI– and, in the case of zaratite, CO32- from the terrestrial environment (CI-bearing akaganeite, bunsenite, goethite, Fe-oxide mineral (Fe2O3) that may be the major cause of the red color on Mars. Coarser-grained gray hematite has the same chemical formula as the red variety, but a different crystalline structure. Deposits of gray hematite found in the Terra Meridiani region of Mars may suggest that water once circulated, hibbingite, lepidocrocite, maghemite, Fe oxide, Fe2+Fe3+2O4, containing oxidized iron (Fe3+) found in the matrix of carbonaceous chondrites and as diagnostic component in CK chondrites. In CK chondrites, magnetite is typically chromian, containing several wt. % Cr2O3., trevorite, and, perhaps, zaratite)
- Opaque form of carbon (C) found in some iron and ordinary chondrites and in ureilite meteorites. Each C atom is bonded to three others in a plane composed of fused hexagonal rings, just like those in aromatic hydrocarbons. The two known forms of graphite, α (hexagonal) and β (rhombohedral), have and More common than taenite, both taenite and kamacite are Ni-Fe alloys found in iron meteorites. Kamacite, α-(Fe,Ni), contains 4-7.5 wt% Ni, and forms large body-centered cubic crystals that appear like broad bands or beam-like structures on the etched surface of a meteorite; its name is derived from the Greek word formed by the decomposition of iron carbide (either Fe-Ni-Co carbide, (Fe,Ni,Co)3C, that occurs as an accessory constituent in several iron meteorites, and coarse octahedrites with < 7 wt. % Ni. or Iron-nickel carbide, (Fe,Ni)23C6, found in iron meteorites.)
- Phosphates formed from schreibersite (apatite, arupite, cassidyite, collinsite, lipscombite, vivianite)
- Sulfates formed by weathering of troilite (honessite, jarosite). Additional phases in irons that formed by terrestrial alteration include metallic Cu, opal, several sulfides (Fe-Ni sulfide, (Fe,Ni)9S8, that is often associated with troilite, and found in the matrix and chondrules of CO, CV, CK and CR chondrites. The color is yellow-bronze with light bronze-brown streak and metallic luster. It typically forms during cooling of magmatic sulfide melts during the evolution of parent silicate melt. The, bornite, chalcopyrite, heazlewoodite, isocubanite), at least two carbonates (reevesite, An obsolete term for an iron meteorite.), a Ni-rich phyllosilicate (pecoraite) and elemental S