Dervillite - Occurrence, Properties, and Distribution

Dervillite is a monoclinic-prismatic brownish-black mineral, containing sulfur, silver, and arsenic.

It was named after Dr. Henri Dervile of Strasbourg University in Strasbourg, France, who observed the original specimen.

Properties of Dervillite

The following are the key properties of Dervillite:

• Cell Data
  • Space Group: P2/a
  • a = 6.833
  • b = 12.932
  • c = 9.638
  • β = 99°33'
  • Z = [8]

• Crystal Data
  • Monoclinic
  • Point Group: 2/m
  • Minute crystals, to 0.3mm
  • X-ray Powder Pattern: 3.075 (10), 3.019 (8), 2.843 (5), 3.251 (3), 2.659 (3), 3.170 (2), 2.742 (2)

• Chemical Composition

  Elements	Content 1	Content 2
  Ag	61.39	60.81
  As	19.03	21.11
  S	18.06	18.08
  Total	98.48	100.00

• Optical Properties
  • Anisotropism: Moderate

• Estimated Properties

  Electron density	Bulk density (electron density) = 2.52 g/cm3 note: Specific gravity of Dervillite = 2.81 g/cm3
  Photoelectric	PEDervillite = 170.89 barns/electron U = PEDervillite x ρElectron density = 430.40 barns/cm3
  Fermion index	Fermion index = 0.0013 Boson index = 0.9986
  Radioactivity	Dervillite is not radioactive

How to Identify Dervillite

Dervillite can be identified by its brownish-black color, having metallic luster, black streak, and good cleavage.

It is opaque, with a relative hardness ranging from 1 to 1.5.

Global Distribution

Dervillite is mainly observed in museum specimens from the Gabe-Gottes mine, Rauenthal, near Sainte-Marie-aux-Mines, Haut-Rhin, France.

Occurrence of Dervillite and Useful Mineral Association

Dervillite occurs in a Co–Ni–Fe–As deposit.

Quartz, calcite, proustite, safflorite, rammelsbergite, and arsenic are the minerals that are closely associated with dervillite.

References

• Dervillite – Mindat
• Dervillite Mineral Data – Webmineral
• Dervillite.pdf - Rruff Project Website - University of Arizona