Emmonsite

Emmonsite, also known as durdenite, is an iron tellurite mineral with the formula: Fe2(TeO3)3·2(H2O).[1] Emmonsite forms triclinic crystals.[1] It is of a yellowish-green color, with a vitreous luster,[1] and a hardness of 5 on the Moh scale.[2]

Emmonsite crystal spray from the Moctezuma Mine (3 mm image width)
Emmonsite
Emmonsite. Locality: San Miguel Mine, Moctezuma, Sonora, Mexico (size: 6.3 x 4.1 x 1.1 cm)
General
CategoryTellurite mineral
Formula
(repeating unit)
Fe2(TeO3)3·2(H2O)
Strunz classification4.JM.10
Crystal systemTriclinic
Crystal classPinacoidal (1)
(same H-M symbol)
Space groupP1
Unit cella = 7.90, b = 8.00
c = 7.62 [Å]; α = 96.73°
β = 95°, γ = 84.47°; Z = 2
Identification
ColorYellowish green
Crystal habitThin to hairlike crystals, occurring in rosettes and sprays; also fibrous globular aggregates and crusts
TwinningNoted
CleavagePerfect on {010}; good on {100} and {001}
Mohs scale hardness5
LusterVitreous
DiaphaneityOpaque to translucent
Specific gravity4.52–4.55
Optical propertiesBiaxial (-)
Refractive indexnα = 1.962 nβ = 2.090 nγ = 2.100 - 2.120
Birefringenceδ = 0.138 - 0.158
PleochroismWeak
2V angleMeasured: 23°
References[1][2][3]

Emmonsite was first described in 1885 for an occurrence in the Tombstone District, Cochise County, Arizona. It was named for the American geologist, Samuel Franklin Emmons, (1841–1911), of the United States Geological Survey.[1][2]

Emmonsite is found, often with quartz or cerussite in the Tombstone, Arizona area.[2] It is also associated with native tellurium, tellurite, native gold, pyrite, rodalquilarite, mackayite, sonoraite, cuzticite and eztlite.[1]

References

  • Frost, Ray L. and Dickfos, Marilla J. and Keeffe, Eloise C. (2008) "Raman spectroscopic study of the tellurite minerals: emmonsite Fe23+Te34+O9.2H2O and zemannite Mg0.5[Zn2+Fe3+(TeO3)3]4.5H2O." Journal of Raman Spectroscopy, 39(12). pp. 1784–1788. Found at Queensland University of Technology website; Accessed September 15, 2010.
  • W. F. Hillebrand, "Emmonsite (?) from a new locality," American Journal of Science, Series 4 Vol. 18, December 1904, P.433-434; doi:10.2475/ajs.s4-18.108.433. Found at AJS Online; Accessed September 15, 2010.
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