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Wurtzite
Current inventory:  0 gems
 

  
Wurtzite was named in 1861 by Charles Friedel in honor of Charles Adolphe Wurtz (1817 - 1884), French chemist who promoted ideas of atomic structure and organic chemistry. Wurtz was a laboratory assistant for Jean Baptiste Dumas at the École de Médecine and was later appointed professor of organic and mineral chemistry and promoted to dean of the college.

Discovered in 1861 ; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

(Zn,Fe)S

Zinc Iron Sulfide

Molecular Weight:

96.50 gm

Composition:

Zinc

60.98 %

Zn

Iron

5.79 %

Fe

Sulfur

33.23 %

S

100.00 %

Classification

Mineral Classification:

Sulfides

Strunz 8th Ed. ID:

2/C.13-10

Nickel-Strunz 10th Ed. ID:

2.CB.45

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

Related to:

Wurtzite Group. Dimorph of Sphalerite. Epitaxial minerals: Chalcopyrite. Trimorphous with Matraite and Sphalerite. Polytypes 2H, 4H, 6H, 8H, 10H, 15R, 18R, and 21R are known.

Members of Group:

Wurtzite Group: Buseckite, Cadmoselite, Greenockite, Rambergite, Wurtzite

Varieties:

Polywurtzite, Voltzite

Synonyms:

Buergerite (of Gagarin and Cuomo), Hurlburtite (of Gagarin and Cuomo), Spiauterite

Crystal Data

Crystallography:

Hexagonal - Dihexagonal Pyramidal

Crystal Habit:

Crystals to 1.5 cm, commonly hemimorphic pyramidal {5052} and {1011}; also short prismatic to tabular {0001}; typically striated horizontally on {1010} and {1011}. The polytypes show steepening of the pyramid as the repeat distance increases along {0001}. As concentrically banded crusts, fibrous or columnar.

Twinning:

None

Physical Properties

Cleavage:

Easy on {1120}; difficult on {0001}.

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

3.5 - 4.0

Density :

3.98 - 4.08; Faceted gems from Merelani measured 3.78 - 3.85.

Luminescence :

May fluoresce orange-red under LW UV. Faceted gems from Merelani were inert under both long- and short-wave UV.

Radioactivity:

Not Radioactive

Optical Properties

Color :

Deep reddish brown, orange-brown or dark brown to brown-black; yellow to dark brown internal reflections common in reflected light.

Transparency:

Transparent to Translucent

Luster :

Resinous, brilliant submetallic on crystal faces

Refractive Index:

2.356 - 2.378  Uniaxial ( + ) 

Birefringence:

0.022

Dispersion :

n/a

Pleochroism:

Very weak, almost invisible

Internal reflections:

Yellow to dark brown

Occurances

Geological Setting:

Of hydrothermal origin in veins with other sulfides. Also along shrinkage fractures in clay-ironstone concretions, of low-temperature origin.

Common Associations:

Sphalerite, Pyrite, Chalcopyrite, Barite, Marcasite.

Common Impurities:

Fe, Cd. May contain up to 8% Fe and 4% Cd.

Type Locality:

San José Mine, Oruro City, Cercado Province, Oruro Department, Bolivia

Year Discovered:

1861

View mineral photos:

Wurtzite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Wurtzite is a zinc iron sulfide mineral that is a less common form of Sphalerite . Wurtzite is trimorphous with Sphalerite and Matraite. Trimorphous means the three minerals have the same basic chemistry but different crystal structures. Opaque Wurtzite is found layered with Sphalerite , Galena  and Marcasite  in Schalenblende . Polished Schalenblende cabochons are available from time to time. Wurtizite has also been found as very small red-brown crystals at the Agios Philippos Mine, Évros Prefecture, Thraki Department, Greece. These crystals are very attractive as mineral specimens but too small for faceting. Wurtzite was not available as faceted, transparent gems until relatively large, bright, gemmy crystals were found in the Winter of 2012 and brought to the market in early 2013. These crystals were found in a single pocket in the  Tanzanite deposit in the Merelani Hills, south of Arusha, Tanzania. The crystals measure up to 2 cm in diameter and have a tabular shape with pyramidal faces. These remarkable crystals are considered to be the best of the species by all who have seen them. There were very few gemmy crystals found making faceted Wurtzite gems very rare.

Other localities: In the USA, from near the Thomaston Dam, Litchfield County, Connecticut; at the Leonard mine, Butte, Silver Bow County, Montana; at Frisco, Beaver County, Utah; and from the Joplin district, Jasper County, Missouri. From Rachelshausen, near Gladenbach, Hesse, Germany. At Liskeard, Cornwall, England. From Mežica (Mies), Serbia. At Príbram,CzechRepublic. In Romania, from Baia Sprie (Felsóbánya). At Quispisiza, near Castro Virreyna, Peru. In a number of mines in the Huanuni district, Oruro, and Chocaya, Potosí, Bolivia.
 

  
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