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Pyrrhotite
Current inventory:  0 gems
 

Chemistry:  Fe_1-x S (x=0 to 0.17)  [Iron Sulfide]

Discovered in 1835;   IMA status: Valid (pre-IMA; Grandfathered).
Pyrrhotite gets its name from the Greek word phrrotes meaning redness in alussion to its color.

Classification

Mineral Classification:

Sulfides

Strunz 8th Ed. ID:

2/C.19-20

Nickel-Strunz 10th Ed. ID:

2.CC.10

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

Related to:

Troilite - Pyrrhotite - Haideite Series

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Crystals typically tabular or platy, to 40 cm; steep pyramidal faces or short pyramidal; as rosettes showing nearly parallel aggregation; commonly massive, granular.

Twinning:

On [1012]

Physical Properties

Cleavage:

None observed; distinct Parting on [0001]

Fracture:

Uneven to Sub-Conchoidal

Tenacity:

Brittle

Hardness (Mohs):

3.5 - 4.5

Hardness (Vickers):

VHN = 373-409 (100g load)

Density:

4.58 - 4.65 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioacitve

Other:

Magnetic; varying in intensity inversely with iron content.

Optical Properties

Color:

Bronze Brown, Bronze Red, or dark Brown; tarnishes quickly, rarely to iridescence

Transparency:

Opaque

Luster:

Metallic

Refractive Index:

n/a  (Opaque)

Birefringence:

n/a  (Opaque)

Dispersion:

n/a  (Opaque)

Pleochroism:

Weak

Anisotropism:

Strong

Occurances

Geological Setting:

Mainly in mafic igneous rocks, typically as magmatic segregations; also in pegmatites, and in high-temperature hydrothermal and replacement veins, and in sedimentary and metamorphic rocks; in iron meteorites.

Common Associations:

Calcite, Chalcopyrite, Dolomite, Magnetite, Marcasite, Pentlandite, Pyrite; and many other sulfides

Common Impurities:

Ni,Co,Cu

Type Locality:

n/a

Year Discovered:

1835

View mineral photos:

Pyrrhotite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Pyrrhotite is a fairly common mineral but rarely faceted as a gem. It is opaque and has a bronzey to brassy color. Pyrrhotite is weakly magnetic. It is the next most common magnetic mineral to Magnetite. Massive Pyrrhotite is common and magnetism is sometimes the only way to distinguish it from other brassy colored sulfides such as Chalcopyrite, Marcasite, Pentlandite or Pyrite. Although massive material occurs at many localities worldwide, good crystals are rare.
 

  
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