Editorial Feature

Erdite - Occurrence, Properties, and Distribution

Erdite is a monoclinic-prismatic mineral, composed of sulfur, sodium, oxygen, iron, and hydrogen. It was first discovered in 1977 from the Coyote Peak diatreme, 16 miles south-west of Orick, Humboldt Co. California.

It was named after Dr. Richard Clarkson Erd, an American mineralogist with the U.S. Geological Survey, who first discovered it.

Properties of Erdite

The following are the key properties of Erdite:

  • Cell Data
    • Space Group: C2/c
    • a = 10.677–10.693
    • b = 9.083–9.115
    • c = 5.499–5.507
    • β = 92°10(2)'-92°23(4)'
    • Z = 4

  • Crystal Data
    • Monoclinic
    • Point Group: 2/m
    • In fine granular, impure masses of minute fibers; single, fine-bladed crystals, to 1mm in length
    • X-ray Powder Pattern: 6.935 (100), 5.342 (71), 4.556 (41), 3.467 (28), 2.310 (23), 2.902 (15), 3.317 (12)

  • Chemical Composition
    Elements Content 1 Content 2 Content 3
    S 40.5 37.6 35.82
    Fe 36.0 34.9 31.20
    Na 14.1 11.2 12.84
    O [9.4] [16.2] 17.88
    K - 0.12 -
    H - - [2.26]
    Total [100.0] [100.02] 100.00

  • Optical Properties
    • Pleochroism: Extreme: brilliant reddish-orange through greenish-grays and pinkish-grays, to dark gray with a barely perceptible bluish or greenish tint
    • Anisotropism: Strong

  • Estimated Properties
    Electron density Bulk density (electron density) = 2.21 g/cm3
    note: Specific gravity of Erdite = 2.22 g/cm3
    Photoelectric PEErdite = 11.26 barns/electron
    U = PEErdite x ρElectron density = 24.86 barns/cm3
    Fermion index Fermion index = 0.009
    Boson index = 0.99
    Radioactivity
    Erdite is not radioactive

How to Identify Erdite

Erdite can be identified in the field by a range of colors, from red to copper-red and black. It has a good cleavage, metallic luster, and black streak.

The density of erdite is 2.3 g/cm3, and its hardness is 2.

Global Distribution

Erdite is distributed in the following places:

  • Mont Saint-Hilaire and near Saint-Amable, Quebec, Canada
  • Mt. Alluaiv, Lovozero massif, Kola Peninsula, Russia
  • Coyote Peak, near Orick, Humboldt Co. California, USA

Occurrence of Erdite and Useful Mineral Association

Erdite occurs in late segregations within an alkalic mafic diatreme, and pegmatites in nepheline syenite.

Minerals such as murmanite, pyrite, bartonite, djerfisherite, rasvumite, magnetite, and pyrrhotite are all closely related to erdite.

References

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