Editorial Feature

Ashanite: Occurrence and Properties

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Ashanite was named after Chinese word ‘Shan’ meaning mountain, in reference to the place of occurrence - Altai Mountains, China.

Chemical Formula - (Nb, Ta,U, Fe,Mn)4O8

Properties of Ashanite

The following are the key properties of ashanite:

Cell Data

  • Space group: Pcan (this describes the symmetry group of a configuration in a three-dimensional space)
  • Cell parameters: a = 5.869Å, b = 4.873 Å, c = 5.216 Å.

Z = 1

Crystal Data

  • Orthorhombic, dipyramidal
  • Point group: 2/m2/m2/m
  • X-ray powder pattern: 2.95 (10), 3.65 (5), 2.54 (3), 2.51 (3), 2.38 (3), 1.729 (3), 2.874 (2)

Chemical Composition

  • Ashanite consists of iron, manganese, niobium, oxygen, tantalum, and uranium.
Elements Content 1
U3O8 23.81
Nb2O5 36.76
Ta2O5 23.41
RE2O3 1.40
FeO 8.25
MnO 7.77
Total 101.40

 

Optical Properties

  • Optical class: Biaxial (+)
  • R1–R2: (440) 12.1–12.1, (460) 11.4–11.5, (480) 11.2–11.3, (500) 11.0–11.0, (520) 11.0–11.0, (540) 10.9–10.9, (560) 10.9–10.8, (580) 10.8–10.8, (600) 10.8–10.7, (620) 10.7–10.7, (640) 10.7–10.6, (660) 10.6–10.6, (680) 10.6–10.6, (700) 10.6–10.6
  • Pleochroism: Weak; X = pale brownish red; Z = dark brownish red
  • Orientation: X = b; Y = a; Z = c
  • Absorption: Z > X
  • α = 2.31 ; β = 2.35; γ = 2.40
  • 2V(meas.) =70°- 75°

Estimated Properties

Electron density Bulk density (electron density) = 5.78 g/cm3
note: Specific gravity of Ashanite = 6.61g/cm3
Photoelectric PEAshanite = 821.10 barns/electron
U=PEAshanite x ρ electron density= 4,748.80 barns/cm3
Fermion index Fermion index = 0.0077313074
Boson index = 0.9922686926
Radioactivity
Ashanite is not radioactive

How to Identify Ashanite

Ashanite can be identified in the field by its color variations such as dark brown and pitch-black. Its opaque form has no cleavage. This mineral has a resinous, sub-metallic luster with brown streaks. The fracture on this mineral is conchoidal, meaning it has a smooth, rounded surface resembling a scallop shell. The density of ashanite is 6.61 g/cm3 with a hardness of 5.5-6.5 on the Mohs scale - between orthoclase, a feldspar, and pyrite.

Occurrence of Ashanite and Useful Mineral Association

Ashanite occurs in the central part of a pegmatite, in albitized two-mica granite. It occurs as single crystals and is often associated with minerals such as tantalum-rich columbite, ishikawaite, and thorium-rich monazite. The species has been discredited by the International Mineralogical Association, who believe it may consist of ixiolite, samarskite, and uranmicrolite.

Sources and Further Reading

This article was updated on 3rd February, 2020.

 

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