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Skutterudite

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Formula:
CoAs3-x
Also given as (Co,Fe,Ni)As2-3.
System:
Isometric
Colour:
Tin-white to ...
Hardness:
5½ - 6
Name:
Named in 1845 by Wilhelm Karl von Haidinger after its discovery locality, Skutterud, Modum, Norway.

The earliest name that possibly refers to any skutterudite-like material, cobaltum eineraceum, was introduced by Georgius Agricola in 1529. Wallerius used several names for a skutterudite-like mineral (kobaltglants, kobaltmalm, minera cobalti cinerea, cobaltum arsenico mineralisatum). Named speiskobalt by Werner (see Hausmann, 1813), but also seemingly equally applied to safflorite and smaltite. Arsenikkobaltkies was used by Karl Johann August Theodor Scheerer for Norwegian skutterudite in 1837 and Arsenikkobalt was used in 1852 by Gustav Rose.

Classification of Skutterudite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
2.EC.05

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
E : Metal Sulfides, M: S <= 1:2
C : M:S = 1:>2
2.12.17.1

2 : SULFIDES
12 : AmBnXp, with (m+n):p = 1:2
3.10.12

3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
10 : Sulphides etc. of Co
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Type Occurrence of Skutterudite

Year of Discovery:
1845

Occurrences of Skutterudite

Geological Setting:
Moderate to high temperature hydrothermal veins

Physical Properties of Skutterudite

Metallic
Diaphaneity (Transparency):
Opaque
Colour:
Tin-white to silver-gray, gray (tarnished)
Streak:
Black
Hardness (Mohs):
5½ - 6
Hardness (Vickers):
VHN100=810 - 915 kg/mm2
Cleavage:
Distinct/Good
Distinct on {001}{111} in traces on {011}
Fracture:
Irregular/Uneven, Conchoidal
Density:
6.5 g/cm3 (Measured)    6.821 g/cm3 (Calculated)

Crystallography of Skutterudite

Crystal System:
Isometric
Class (H-M):
m3 (2/m 3) - Diploidal
Space Group:
Im3
Cell Parameters:
a = 8.204Å
Unit Cell Volume:
V 552.18 ų (Calculated from Unit Cell)
Z:
8
Morphology:
Cubic crystals
Twinning:
On {112} as sixlings, reported on {011}

Crystallographic forms of Skutterudite

Crystal Atlas:
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Skutterudite no.1 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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Edge Lines | Miller Indicies | Axes

Transparency
Opaque | Translucent | Transparent

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Along a-axis | Along b-axis | Along c-axis | Start rotation | Stop rotation
X-Ray Powder Diffraction:
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Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Chemical Properties of Skutterudite

Formula:
CoAs3-x

Also given as (Co,Fe,Ni)As2-3.
Essential elements:
All elements listed in formula:
Analytical Data:
Fe,Ni,S
Common Impurities:
S,Bi,Cu,Pb,Zn,Ag,Fe,Ni

Relationship of Skutterudite to other Species

Series:
Forms a series with Nickelskutterudite (see here)
Other Members of Group:
3.10.1Cobaltpentlandite(Co,Ni,Fe)9S8
3.10.2LinnaeiteCo2+Co23+S4
3.10.3CattieriteCoS2
3.10.4FrebolditeCoSe
3.10.5BornhardtiteCo2+Co23+Se4
3.10.6TrogtaliteCoSe2
3.10.7Hastite
3.10.8MattagamiteCoTe2
3.10.9Modderite(Co,Fe)As
3.10.10Safflorite(Co,Ni,Fe)As2
3.10.11ClinosaffloriteCoAs2
3.10.13CobaltiteCoAsS
3.10.14ParacostibiteCoSbS
3.10.15CostibiteCoSbS
3.10.16AlloclasiteCo1-xFexAsS
3.10.17Glaucodot(Co0.50Fe0.50)AsS
3.10.18CarrolliteCu(Co,Ni)2S4

Other Names for Skutterudite

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Skutterudite

Reference List:
Georgius Agricola in 1529.
Wallerius
Werner
Hausmann, 1813
Breithaupt, A. (1827): Ueber eine neue Kies-Spezies von Skutterud. Annalen der Physik und Chemie 9: 115-116 [Tesseralkies, Hartkobaltkies]

Scheerer, T. (1837): Ueber zwei norwegische Kobalterze von den Skutteruder Gruben. Annalen der Physik und Chemie 42: 546-555. [Arsenik-kobaltkies]

Hausmann, J. F. L. (1847): Handbuch der Mineralogie. Zweiter Theil. System und Geschichte der Mineralkörper, 2nd edition. p. 69. [Hartkobalterz]

Haidinger, W. (1845): Handbuch der bestimmenden Mineralogie, enthaltend die Terminologie, Systematik, Nomenklatur und Charakteristik der Naturgeschichte des Mineralreiches, 650 pp. Braumüller & Seidel, Wien, p. 560. [Skutterudit]

Nicol, J. (1849): Manual of Mineralogy or the Natural History of the Mineral Kingdom. Adam and Black, Edinburg, p. 457. [Modumite]

Samdahl, B. (1925): Analyse der Skutterudits. Norsk Geologisk Tidsskrift. 8, 63-73

Oftedal, I. (1926): The crystal structure of skutterudite and related minerals. A preliminary paper. Norsk Geologisk Tidsskrift 8: 250-257 + plate.
[http://foreninger.uio.no/ngf/ngt/pdfs/NGT_08_4_250-257.pdf]

Oftedal, I. (1928): Die Kristallstruktur von Skutterudit und Speiskobalt-Chloanthit. Zeitschrift für Kristallographie 66: 517-546.

Palache, Charles, Harry Berman & Clifford Frondel (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged: 342-347.

Holmes, R.J., 1947. HIGHER MINERAL ARSENIDES OF COBALT, NICKEL, AND IRON.
BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA. VOL. 58, PP. 299-392.

Roseboom, E.H. (1962): Skutterudites (Co,Ni,Fe)As3-x: Composition and cell dimensions. American Mineralogist, 47, 310-327.

Klemm, D.D. (1965): Untersuchungen mit der Elektronenmikrosonde über die natürlichen Mischkristallbereiche der Skutterudite. Contributions to Mineralogy and Petrology 11, 323-333.

Radcliffe, D. (1968): Structural formula and composition of skutterudite. Can. Mineral. 9, 559-563.

Canadian Mineralogist (1971): 9: 559.

Acta Crystallographica: B27: 2288-2289.

Internet Links for Skutterudite

Specimens:
The following Skutterudite specimens are currently listed for sale on minfind.com.

Localities for Skutterudite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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