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The Mineral wurtzite

Hexagonal Wurtzite Plate

Wurtzite is a rare, high temperature polymorph of the common mineral Sphalerite. It forms at temperatures above 2192º F (1200º C) as hexagonal crystals. An ornamental stone known as Schalenblende (an intergrowth of Wurtzite, Sphalerite, and often Galena) is usually referenced with Wurtzite but is more often listed as a variety of Sphalerite.

Chemical Formula

ZnS
This above is the formula for pure Wurtzite. However, since it often has some iron replacing the zinc, its formula is more accurately described as (Zn,Fe)S

Color

Light to dark brown

Crystal System

Hexagonal

Properties

Streak
Light brown

Hardness
3.5 - 4

Transparency
Translucent to nearly opaque

Specific Gravity
4

Luster
Resinous

Cleavage
2,1 - basal ; 3,1 - prismatic

Fracture
Uneven

Tenacity
Brittle

Crystal Habits

Occurs in pyramidal crystals, often striated or with growth layers. Also occurs as short prismatic and tabular crystals, in capillary groupings, as fibrous and columnar masses, and in compacted aggregates.

3D Crystal Atlas

Additional Information

Composition
Zinc sulfide

In Group
Sulfides; Simple Sulfides

Striking Features
Streak, color, and unique crystal habits

Environment
In hydrothermal deposits usually in the sulfide zone.

Rock Type
Sedimentary, Metamorphic

Varieties

Schalenblende

- Banded form of Sphalerite and Wurtzite often associated with Galena (and sometimes Pyrite). The term Schalenblende is occasionally incorrectly used as a synonym for Wurtzite.

Uses

Wurtzite is a very rare mineral, and only of value to scientists and mineral collectors. Schalenblende is used as a rare ornamental stone.

Noteworthy Localities

Large Wurtzite crystals come from two Bolivian mines: the San Jose Mine, Oruro; and the Siglo Veinte Mine, Llallagua, Potosi Department. Good European localities include Carrara, Tuscany, Italy; the Les Malines Mine, Saint-Laurent-le-Minier, Gard, France; Kirki, Thrace, Greece; and Pribram, Bohemia, Czech Republic. Wurtzite is also found in China in the Yaogangxian Mine, Hunan Province. A small finding of large, translucent, reddish-brown crystals, which many consider to be the best of species, have come from a recent find in the Merelani Hills, Arusha, Tanzania.

In the U.S., Wurtzite comes from Butte, Silver Bow Co., Montana; Frisco, Beaver Co., Utah; the Thomaston Dam, Litchfield Co., Connecticut; Negley, Columbiana Co., Ohio; and in the the lead mines of Reynolds Co., Missouri. Small amounts were also found in the Sterling Hill Mine in Ogdensburg, Sussex Co., New Jersey; and in Ellenville, Ulster Co., New York.