Phosphide minerals are common accessory phases in a variety of interplanetary dust particles. They are also found in Earth’s igneous and sedimentary rocks.
Fe-Ni phosphides can be formed with relatively high temperatures, as well as with highly reducing geochemical conditions. In general, terrestrial phosphides are nickel-poor, and their composition varies from 2 to 3 percent Fe. Meteoritic phosphides are much more nickel-rich, with a range of 0.3 to 4.5 percent Fe.
The most abundant of all phosphide minerals is schreibersite, which occurs as a matrix element in kamacite and silicate. In a recent study, five new minerals were identified in this system.
Phospaherite, a phosphate with eight electrons, was discovered in natural environmental samples. It is not known if it can be used as a biological feedstock molecule. However, it has been shown that phosphite participates in metabolic pathways, and it has been suggested that it is an electron shuffle molecule.
A variety of meteoritic phosphides have been characterized, including apatite, trevorite, schreibersite, taenite, and enstatite. Five of these are new to science, while the remaining four are common in nature.
Iron-nickel phosphides have been discovered in the northern Negev Desert, Israel. These are the first terrestrial occurrences to be rich in iron, nickel, and phosphorus. This mineralization is associated with a large chain of black phosphide grains.
In addition to these four, there are five other minerals in the ternary Fe-Ni-P system. The other minerals are apatite, barringerite, nickelphosphide, schreibersite, and taenite.
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