Cobaltite
Current inventory:  0 gems
 

  
Cobaltite is named for its elemental composition containing Cobalt. Cobalt is named from the German, Kobold, "underground spirit" or "goblin," in allusion to the refusal of cobaltiferous ores to smelt properly, hence "bewitched."

Discovered in 1832; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

CoAsS

Cobalt Arsenic Sulfide

Molecular Weight:

165.92 gm

Composition:

Cobalt

35.52 %

Co

Arsenic

45.16 %

As

Sulfur

19.33 %

S

100.00 %

Classification

Mineral Classification:

Sulfides

Strunz 8th Ed. ID:

2/D.18-10

Nickel-Strunz 10th Ed. ID:

2.EB.25

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
E : Metal Sulfides, M: S <= 1:2
B : M:S = 1:2, with Fe, Co, Ni, PGE, etc.

Related to:

Cobaltite Group. Cobaltite - Ullmannite - Tolovkite Series. Chemically very similar to Glaucodot and Alloclasite.

Members of Group:

Cobaltite Group:

Varieties:

None

Synonyms:

None

Crystal Data

Crystallography:

Orthorhombic - Pyramidal

Crystal Habit:

Commonly as pseudocubic or pseudopyritohedral crystals, or combinations having striated faces as with pyrite, to as large as 8 cm, also as pseudo-octahedra; granular massive.

Twinning:

About {111} as a pseudocubic three-fold axis, with {011} and {111} of the pseudocubic habit as twin planes, rare. Twin lamellae are commonly observed in polished section, which may exhibit a flamelike texture.

Physical Properties

Cleavage:

Perfect on {001}

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

5.5

Density:

6.33 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Health Warning:

CAUTION: Contains Arsenic, a poisonous element - always wash hands after handling. Avoid inhaling dust when handling or breaking. Never lick or ingest.

Optical Properties

Color:

Silvery White to Reddish Silvery White, Violet Steel Gray, or Black

Transparency:

Opaque

Luster:

Metallic

Refractive Index:

R: (400) 48.2, (420) 48.0, (440) 47.7, (460) 47.8, (480) 48.2, (500) 48.9, (520) 49.6, (540) 50.4, (560) 51.2, (580) 51.9, (600) 52.6, (620) 53.1, (640) 53.5, (660) 53.7, (680) 53.8, (700) 53.8

Birefringence:

None; Opaque

Dispersion:

None; Opaque

Pleochroism:

Very weak; on grain boundaries

Occurances

Geological Setting:

In high-temperature hydrothermal deposits, as disseminations, and as veins in contact metamorphosed rocks.

Common Associations:

Allanite, Calcite, Chalcopyrite, Magnetite, Scapolite, Skutterudite, Sphalerite, Titanite, Zoisite (Tunaberg, Sweden); numerous other Co–Ni sulfides and arsenides.

Common Impurities:

Cu, Pb, Sb, Fe, Ni

Type Locality:

Unknown; possibly Cobalt, Coleman Township, Timiskaming District, Ontario, Canada; or Tunaberg, Nyköping, Södermanland, Sweden

Year Discovered:

1832

View mineral photos:

Cobaltite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Cobaltite is a rare sulfide mineral that is opaque and metallic. It is occasionally available as cabochons from massive material and rarely faceted. A faceted gem would be a rare curiosity for collectors. Cabochons and faceted gems are attractive due to the beautiful reddish, silvery metallic appearance of the mineral. Some natural pseudopyritohedral crystals may appear to have been roughly faceted by Mother Nature.

Cobaltite deposits often have a weathering crust of minerals such as Erythrite. Since cobalt is a strong coloring metal, minerals like Erythrite are strongly colored, in this case deep pink to bright purple. Miners called these colorful minerals "cobalt blooms" and used them as indicators of the presence of cobalt ores such as Cobaltite.

Fine, well shaped crystals are available from Columbus Mine, Cobalt, Coleman Township, Timiskaming District, Ontario, Canada; Tunaberg, Nyköping, Södermanland, Sweden; Håkansboda, Lindesberg, Västmanland, Sweden; and Riddarhyttan, Skinnskatteberg, Västmanland, Sweden.
 

  
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