Allabogdanite – a very rare phosphide mineral

Allabogdanite is a very rare phosphide mineral with the formula (Fe, Ni)2P, found in 1994 in a meteorite. It is the only known natural high-pressure phase reported in the Fe–Ni–P system. It is an orthorhombic-dipyramidal light straw yellow mineral containing cobalt, iron, nickel, and phosphorus.

It was described for an occurrence in the Onello meteorite in the Onello River basin, Sakha Republic; Yakutia, Russia; associated with taenite, schreibersite, kamacite, graphite and awaruite. It was named for Russian geologist Alla Bogdanova.

General information

  • Category: Phosphide mineral
  • Formula: (Fe,Ni)2P
  • Crystal system: Orthorhombic
  • Crystal class: Dipyramidal (mmm)
  • Color: Light straw-yellow.

Properties

Crystals of the mineral, up to 0.4 × 0.1 × 0.01 mm, are flattened on (001) with dominant {001} faces, and other faces that are probably {110} and {100}. Crystals are light straw-yellow with bright metallic luster. Moh’s hardness is 5–6; the mineral is very brittle, and its calculated density 7.10 g/cm3.

  • Crystal habit: Minute exolution laminae in plessite
  • Tenacity: Brittle
  • Mohs scale hardness: 5-6
  • Luster: Metallic
  • Diaphaneity: Opaque
  • Specific gravity: 7.11

Occurrences

The occurrence of allabogdanite in Santa Catharina, one of the largest and well-studied meteorites, suggests that this mineral is more common than was believed. The formation of allabogdanite-bearing phosphide assemblages in a given meteorite provides evidence that it experienced peak pressure of at least 8 GPa at a temperature above 800 °C.

It occurs as thin lamellar crystals disseminated in plessite. Associated minerals are nickelphosphide, schreibersite, awaruite, and graphite.

The mineral is named for Alla Bogdanova, Geological Institute, Kola Science Centre of Russian Academy of Sciences. It was named in honor of Alla Nikolaevna Bogdanova (1947 – 2004), crystallographer with the Geological Institute, Kola Science Centre of Russian Academy of Sciences, Apatity, Kola peninsula, Russia, for her contributions to the study of new mineral species.

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