Sphalerite Value, Price, and Jewelry Information


Star of Asturias - sphalerite
“The Star of Asturias,” 163.4 cts, the largest known faceted sphalerite, on display at the Cantonal Museum of Geology, Lausanne, Switzerland, by Sailko. Licensed under CC By 3.0. (Cropped to show detail).

Sphalerite occurs in many colors, including green, yellow, orange, brown, and fiery red. With a dispersion over three times that of diamond and an adamantine luster, faceted specimens make beautiful additions to gem collections. However, they're too soft for most jewelry uses.

Sphalerite Value

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Sphalerite Value via Gem Price Guide
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Sphalerite Information

DataValue
NameSphalerite
Crystallography Isometric. Crystals widespread, in various shapes; massive, cleavable, granular.
Refractive Index 2.50 to 2.396
Luster Resinous to adamantine.
Fracture Brittle.
Hardness 3.5 to 4
Specific Gravity 3.90 - 4.10
Cleavage Perfect dodecahedral.
Dispersion 0.156 (extremely high).
Heat SensitivityYes
Luminescence Bright orange-red to red in LW, SW, from many localities. Material from Otavi, Namibia is triboluminescent. (Produces light under friction).
Wearability Poor
Enhancements None
Transparency Opaque to transparent.
Absorption Spectrum Sometimes 3 bands seen in the red at 6900, 6670. and 6510 due to cadmium.
FormulaZnS + Fe
Optics Isotropic; N = 2.37-2.43. (Spanish material 2.40).
EtymologyFrom the Greek sphaleros, meaning “treacherous,” because sphalerite often resembles galena (lead sulfide) but yields no lead.
OccurrenceSphalerite is the chief ore of zinc, the most abundant zinc mineral, and is common in low-temperature ore deposits, especially in limestones; also in sedimentary rocks; hydrothermal ore veins.
sphalerite - faceted collection
Sphalerite: Colorado (1.93). Spain (3.30), Mexico (4.65) // Spain (14.48, 5.57). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Comments

You’ll find no shortage of facetable sphalerite rough in most colors. Faceting this material, however, poses a challenge. Sphalerites have a low hardness (3.5 to 4) and perfect cleavage.

Iron-rich, opaque, black stones are known as marmatites, named after the locality, Marmato, Italy. In Europe, sphalerite is sometimes called blende, after the German word blenden, “to dazzle.” Though they have no connection to actual ruby gems, stones with red and orange shades are sometimes called “ruby blende.” Low-iron, pale and colorless sphalerites, known as cleiophanes, are extremely rare.

RI and SG vs Sphalerite Chemical Composition
Refractive index (N) and specific gravity plotted against chemical composition in sphalerite, in which Fe substitutes for Zn, in the formula (Zn,Fe)S. Adapted from W. A. Deer, R. A. Howie, and J. Zussman, 1962, Rock Forming Minerals, vol. 5 (New York: Wiley), p. 174.

A number of trace elements may contribute to color in sphalerites. These include germanium, calcium, copper, mercury, and cerium (yellow); tin, silver, and molybdenum (reddish); and cobalt and iron (green).

Sphalerite and wurtzite are polymorphs. They share the same chemical formula (ZnS), but have different crystal habits. Sphalerite has an isometric crystal structure, while wurtzite has a hexagonal structure. These two minerals can coexist in alternating layers as schalenblende, a gem material used rarely for cabochons.

schalenblende - sphalerite and wurtzite mix
“Schalenblende” by Ra’ike. Licensed under CC By-SA 3.0.

Identifying Characteristics

Sphalerites may have a streak color ranging from pale brown to yellow or white. Keep in mind that streak testing can destroy the test sample. Conduct this examination only as a last resort for gem identification on rough, never on a finished gem. This test will also release a sulfurous odor from the test sample.

Sphalerites are pyroelectric. When heated, these gems generate an electrical charge.

Sphalerites may show anomalous double refraction due to crystal strain.

Synthetics

Since sphalerite ranks as the primary ore for zinc mining, scientists have synthesized this mineral for industrial research. In addition, facetable synthetic sphalerites in all their colors have appeared in jewelry and gem collections.

Enhancements

No known gemstone treatments.

Polishing scratches on the bottoms of sphalerite cabochons may cause apparent chatoyancy and asterism. (Although these scratches may occur accidentally, be aware that sphalerites don’t normally display these phenomenal effects).

Sources

Significant gem-quality sources include:

  • Santander, Spain: major gem locality, large cleavages of red-orange color.
  • Cananea, Sonora, Mexico: fine green transparent material, often pale colored and color zoned, sometimes yellow.
  • Kipushi, Zaire: dark green material containing elevated amounts of cobalt and iron.
  • United States: Franklin, New Jersey (almost colorless to pale green, transparent variety known as cleiophane); Kansas/Missouri/Oklahoma (so-called Tri-State Region, heavily mineralized by lead and zinc, with many localities and operating mines); Tiffin, Ohio (red color); Colorado/Utah (may be transparent); Arizona; Idaho; Montana; Wisconsin.
  • Australia; Canada; China; Czech Republic; England; France; Germany; Tsumeb, Namibia; Romania; Scotland; Sweden
sphalerite - China
“Sphalerite,” Huanggang Mines, near Chifeng, Inner Mongolia, China, 4.1 x 3.0 x 2.3 cm. © Rob Lavinsky, www.iRocks.com. Used with permission.

Stone Sizes

From the large, reddish material from Spain, faceters could easily cut gems of hundreds of carats, as well as cabochons. Green cleiophane material from New Jersey has yielded faceted gems as large as 15 carats. Mexican material could yield faceted gems to 50 carats.

  • Smithsonian Institution (Washington, DC): 73.3, 68.9 (yellow-brown. Utah); 59.5 (yellow-green, New Jersey): 48 (yellow, Mexico); 61.9, 45.9 (yellow, Spain).
  • California Academy of Sciences (San Francisco): 150.3 (dark red-brown oval, Spain).
  • National Museums of Canada (Ottawa, Ontario): 100.1 (dark orange, round, Spain).
  • Private Collection: 24.8 (gray-green, Mt. Ste. Hilaire, Quebec).

Care

Clean sphalerites only with a soft brush, mild detergent, and warm water. See our Gemstone Jewelry Cleaning Guide for more recommendations.

sphalerite - New York
“Sphalerite,” Balmat-Edwards Zinc District, St Lawrence Co., New York, USA, 2.75 x 1.75 x 1.5 cm. © Rob Lavinsky, www.iRocks.com. Used with permission.