The crystallographic orientation of carlsbergite (CrN) in the north Chile meteorite (hexahedrite) was investigated using electron backscatter diffraction and transmission electron microscopy. These studies examined the CrN crystals in the rhabdites (idiomorphic schreibersite) and in kamacite. It was found that the CrN crystals embedded in rhabdite show a number of different orientation relationships with the host crystals. These orientations can be explained based on the lattice dimensions of both coexisting crystalline materials. It was also found that both carlsbergite and kamacite are characterized by a high dislocation density (≥ l09 cm-2) while rhabdite is free of dislocations. It is supposed that in spite of the deformed metallic matrix, a general connection between the orientation relation of all the phases involved exists.

Moraskoite, a new natural phosphate of composition Na2Mg(PO4)F, has been found in the Morasko IAB-MG iron meteorite. The new phosphate occurs in a graphite-troilite inclusion enclosed in a kamacite-taenite matrix. Associated minerals in the inclusions are chlorapatite, buchwaldite, brianite, merrillite, a new phosphate phase of composition Na4MgCa3(PO4)4, chromite, enstatite (bronzite), kosmochlor, kosmochlor–augite, olivine, albite, orthoclase, quartz, cohenite, schreibersite, nickelphosphide, altaite, pyrrhotite, sphalerite, daubreelite, djerfischerite, whitlockite and native Cu. The inclusions are rimmed by a schreibersite-cohenite halo. Moraskoite forms aggregates up to 1.5 mm in size, with individual grains 20–300 μm across. It is colourless and transparent, with a white streak and vitreous lustre; fluorescence is weak blue in ultraviolet radiation (254 and 360 nm); hardness is 4–5; it has irregular, conchoidal fracture and cleavage is rarely observed. Calculated density (using the empirical formula) is 2.925 g cm–3. The moraskoite structure (Pbcn, a = 5.2117(10), b = 13.711(3), c = 11.665(2) Å, V = 833.6(3) Å3 and Z = 8) is similar to that of its synthetic analogue. The strongest diffraction lines of the moraskoite powder diffraction pattern are as follows (dhkl, I): 3.909(75), 3.382(52), 2.955(90), 2.606(100), 2.571(96), 2.545(68), 1.691 (67). In the Raman spectrum, the following characteristic bands are distinguished (cm–1, strong bands bold): 1114, 1027, 962, 589, 438, 336, 308, 279, 262, 244, 193, 184, 147 and 131. The Raman data prove the absence of H2O and CO2. Moraskoite is interpreted as being a primary phosphate, which crystallized together with graphite, troilite and other accessories inside the nodule.

The recently discovered Agoudal impact site in Morocco is a small, eroded impact structure with well-developed shatter cones. A scanning electron microscopic study of a shatter cone surface has revealed the presence of schreibersite – a phosphide very rare on Earth but common in iron meteorites – and Fe–Ni oxides. This is the first reported evidence for primary meteoritic matter adherent to shatter cones and suggests that the Agoudal crater was formed by the impact of an iron meteorite, probably the Agoudal IIAB iron. Shatter cones from other terrestrial impact structures might also hold valuable information about the nature of the impacting projectiles.

The mineral schreibersite, (Fe,Ni)3P, a ubiquitous component of iron meteorites, is known to undergo anoxic hydrolytic modification to afford a range of phosphorus oxyacids. H-phosphonic acid (H3PO3) is the principal hydrolytic product under hydrothermal conditions, as confirmed here by 31P-NMR spectroscopic studies on shavings of the Seymchan pallasite (Magadan, Russia, 1967), but in the presence of photochemical irradiation a more reduced derivative, H-phosphinic (H3PO2) acid, dominates. The significance of such lower oxidation state oxyacids of phosphorus to prebiotic chemistry upon the early Earth lies with the facts that such forms of phosphorus are considerably more soluble and chemically reactive than orthophosphate, the commonly found form of phosphorus on Earth, thus allowing nature a mechanism to circumvent the so-called Phosphate Problem.

This paper describes the Galvanic corrosion of Fe3P, a hydrolytic modification pathway for schreibersite, leading again to H-phosphinic acid as the key P-containing product. We envisage this pathway to be highly significant within a meteoritic context as iron meteorites are polymetallic composites in which dissimilar metals, with different electrochemical potentials, are connected by an electrically conducting matrix. In the presence of a suitable electrolyte medium, i.e., salt water, galvanic corrosion can take place. In addition to model electrochemical studies, we also report the first application of the Kelvin technique to map surface potentials of a meteorite sample that allows the electrochemical differentiation of schreibersite inclusions within an Fe:Ni matrix. Such experiments, coupled with thermodynamic calculations, may allow us to better understand the chemical redox behaviour of meteoritic components with early Earth environments.