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Chemical Formula | ZnS This is the formula for pure Sphalerite. However, since it usually occurs with some iron replacing the zinc, its formula is scientifically recognized as: (Zn,Fe)S |
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Composition | Zinc sulfide, usually with some iron, sometimes with magnesium, manganese. In some localities, it contains cadmium, indium, and gallium. | ||||||||||
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Variable Formula | (Zn,Fe)S ; (Zn,Fe,Mg,Mn,Cd,In,Ga)S |
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Color | Black, brown, red, orange, yellow, green, gray. Rarely colorless. Some specimens contain crystals of different colors, and there is a brown, globular, banded variety. | ||||||||||
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Streak | Pure Sphalerite has a white streak. However, impurities are almost always present, giving this mineral a light brown streak. The streak is always a lighter color than the specimen. | ||||||||||
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Hardness | 3½ - 4 | ||||||||||
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Crystal Forms and Aggregates |
(Isometric) Most commonly as tetrahedral crystals, which are usually twinned and grouped together. They may closely resemble octahedral crystals. Also occurs as groupings of distorted dodecahedral and cubic crystals. Crystal faces are usually rounded or curved. Also occurs massive, grainy, botryoidal, stalactitic, and as large, distorted cleavage fragments. | ||||||||||
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Transparency | Transparent to opaque | ||||||||||
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Specific Gravity | 3.9 - 4.1 | ||||||||||
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Luster | Metallic, submetallic, adamantine, resinous | ||||||||||
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Cleavage | 1,all sides, forming a dodecahedron | ||||||||||
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Fracture | Conchoidal | ||||||||||
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Tenacity | Brittle | ||||||||||
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Other ID Marks | 1) Some transparent or translucent varieties
fluoresce orange in shortwave ultraviolet light 1) Commonly triboluminescent |
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Other Names |  Blende, Zinc
Blende, Black Jack |
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Varieties | Cleiophane - Transparent,
colorless or lightly colored variety Marmatite
- Opaque, metallic-lustered, iron-rich variety Ruby
Jack - Red variety |
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Polymorphs | Wurtzite | ||||||||||
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In Group | Sulfides ; Simple sulfides | ||||||||||
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All About | Sphalerite is a common mineral, and occurs in many different colors. Iron impurities are almost always present in this mineral, and for this reason it is rarely transparent. If Sphalerite contains a large amount of iron impurities, it will be a metallic dark gray or black color, which is typical of most sulfide minerals. | ||||||||||
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Uses | Sphalerite is the main ore of zinc. In some localities, it occurs with significant amounts of cadmium, gallium, and iridium, and it is also the main ore of those metals. Sphalerite is an important mineral to collectors, and some transparent varieties are occasionally faceted for collectors. | ||||||||||
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Striking Features | Color and luster, crystal forms, and streak | ||||||||||
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Complex Tests | Dissolves in hydrochloric acid, producing a sulfurous, rotten-egg odor | ||||||||||
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Popularity (1-4) | 2 | ||||||||||
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Prevalence (1-3) | 1 | ||||||||||
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Demand (1-3) | 1 | ||||||||||
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Distinguishing Similar Minerals |
Galena - heavier (7.4 - 7.6), has a gray
streak, has a distinct bluish metallic color Siderite - lacks brown streak, has different crystals and cleavage Tetrahedrite - has a dark gray streak Argentite - has a shiny black streak, is sectile and malleable |
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Commonly Occurs With |
Galena, Fluorite, Dolomite, Quartz, Calcite, Chalcopyrite, Pyrite, Barite, Argentite, Greenockite | ||||||||||
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Noteworthy Localities |
Sphalerite is a rather common mineral, and
there are many localities where fine specimens have come
from. Worldwide, the most notable occurrences are Trepca,
former Yugoslavia; Alston Moor, England; Binnental,
Wallis, Switzerland; and Broken Hill, New South Wales,
Australia. Spectacular transparent yellow, orange, and
red crystals come from Santander, Spain. In Mexico, large iron-rich, metallic-lustered crystals associated with Galena were found in Mazapil, Zacatecas, and green crystals, often twinned, in Cananea, Sonora. In the U.S., some of the finest specimens come from the tri-state mining district of Missouri, Kansas, and Oklahoma. These areas include the Joplin area, Jasper Co., Missouri; Treece, Galena, and Baxter Springs, Cherokee Co., Kansas; and Picher, Ottawa Co., Oklahoma. Much Sphalerite has come from the Balmat area, St. Lawrence Co., New York; and dark green crystals from the Iron Cap Mine in Graham Co., Arizona. Many specimens are from Franklin and Ogdensburg, Sussex Co., New Jersey, including pale green Cleiophane crystals. Superb examples of this mineral were found in the Elmwood Mine, Carthage, Smith Co., Tennessee. The Fluorite mines of Hardin Co., Illinois, have also produced quality Sphalerite. Lustrous brownish crystals are also found in the Redland Quarry, Niagara Falls, New York. In Canada, good examples of this mineral come from Mont Saint Hilaire, Quebec. |
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Picture Icon Links |
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Picture Links | 1. "Ruby
Jack" 2. Sphalerite on Dolomite 3. Distorted single crystal 4. Iron rich, metallic-lustered "Marmatite" 5. Mass of reddish brown crystals 6. Green Sphalerite crystal |
