Smithsonite Value, Price, and Jewelry Information

A bi-color pink and medium green-blue smithsonite, divided by a colorless band. 24.40-ct, triangular cabochon, 23.5 x 12.9 mm, Choix, Sinaloa, Mexico. © The Gem Trader. Used with permission.

Smithsonite

Smithsonite occurs across the globe, but facetable crystals are extremely rare. These gems can show a wide range range of rich colors but are too soft for most jewelry use. However, high dispersion makes properly faceted smithsonites truly magnificent collector’s pieces.

Smithsonite Information

Data Value
Name Smithsonite
Crystallography Hexagonal (R). Crystals rhombohedral; massive, botryoidal, compact, stalactic.
Refractive Index 1.621-1.848
Colors White, gray, pale to deep yellow, yellowish brown to brown, pale green, apple green, blue-green, blue, pale to deep pink, purplish, rarely colorless. May show color zoning.
Luster Vitreous to pearly, earthy, dull.
Hardness 4-4.5
Fracture Uneven
Specific Gravity 4.3-4.45
Birefringence 0.227
Cleavage Perfect rhombohedral
Dispersion 0.037
Luminescence See "Identifying Characteristics" below.
Luminescence Present Yes
Luminescence Type Fluorescent, UV-Long, UV-Short
Enhancements Oiling, surface coating.
Typical Treatments Oiling, Surface Coating
Transparency Translucent to opaque.
Absorption Spectrum Not diagnostic.
Formula ZnCO3 + Fe, Ca, Co, Cu, Mn, Cd, Mg, Pb.
Optics = 1.848; e = 1.621. Uniaxial (-).
Optic Sign Uniaxial -
Etymology After James Smithson, the British mineralogist who discovered that the zinc ore known as calamine was composed of two distinct minerals, later named hemimorphite and smithsonite.
Occurrence Commonly occurs as a secondary mineral in the oxidized zone of zinc-bearing deposits.
smithsonite specimens from the Smithsonian Institution

In addition to identifying smithsonite as a distinct mineral in 1802 and other scientific accomplishments, James Smithson was the founding donor and namesake of the Smithsonian Institution. Three specimens of smithsonite, center specimen from Greece, the other two from Namibia, from the collection of the Smithsonian Institution. Photo credit: Laurie Minor-Penland. Public.Resource.Org. Licensed under CC By 2.0.

Comments

Smithsonite belongs to the calcite mineral group. It also forms a series as the zinc-dominant (Zn) end member with iron-dominant (Fe) siderite.

For many years, collectors have prized blue-green smithsonites from New Mexico and yellowish stones from Tsumeb, Namibia. However, varieties in many stunning colors exist, including deep yellows, apple greens, pinks, and purples.

smithsonite crystal - Mexico

Smithsonite, 10.0 x 8.5 x 5.2 cm. Refugio Mine, Choix, Sinaloa, Mexico. © Rob Lavinsky, www.iRocks.com. Used with permission.

Some references may cite traces of cadmium as the cause of yellow, cobalt as the cause of pink, and copper as the cause of green and blue. However, research on the causes of color in this gemstone continues. For example, some pink specimens identified as “cobaltian smithsonites” proved to have no cobalt under further examination.

Regardless of the causes, the colors of faceted smithsonites benefit greatly from this gem’s considerable dispersion or “fire.” Unfortunately, relatively low hardness and perfect cleavage leave these gems vulnerable to damage from everyday wear as jewelry stones. Furthermore, the cleavage can also make smithsonites difficult to cut.

cut smithsonite gems - Namibia

Smithsonite: Tsumeb, Namibia (cabochon ~ 50, faceted gems ~ 18, 12). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Identifying Characteristics

Smithsonite effervesces in warm acids. Please keep in mind that acid testing is a destructive test. It can endanger both the gem and the tester. Never conduct this test on a finished gem. Use this procedure on rough as a last resort for gem identification only.

Birefringence

Faceted smithsonites may show a doubling of back facets as seen through the table due to high birefringence. However, such stones must have considerably greater transparency than typical.

Cabbed smithsonites will show a “birefringence blink” when examined through a refractometer.

emerald-cut smithsonite - Namibia

Smithsonite: Tsumeb, Namibia (3.16). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Luminescence

Under shortwave ultraviolet light:

  • Medium whitish blue (Japan).
  • Blue-white (Spain).
  • Rose red (England).
  • Brown (Georgia, Sardinia).

Under longwave ultraviolet light:

  • Greenish yellow (Spain).
  • Lavender (California).

Synthetics

Geologists have synthesized smithsonite (a zinc ore) for research purposes. Evidently, “synthetic smithsonite” does occasionally appear in jewelry. However, an online search for such pieces doesn’t clarify whether this material is actually lab created or just a simulant or “imitation.” These may be instances of the term “synthetic” used in the more popular sense of just simply “not real.”

Enhancements

Smithsonites are somewhat porous. Thus, some pieces may receive oil treatments to enhance their luster or surface coatings to prevent discoloration.

Sources

The Kelly Mine in Socorro County, New Mexico, USA produces celebrated blue and blue-green material of fine color in massive crusts.

Smithsonite crystals - Mexico and New Mexico

Smithsonite: Kelly Mine, New Mexico (blue 5 inches), Mexico (other colors). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Most facetable material comes from African sources. Tsumeb, Namibia produces yellowish, pinkish, and green facetable crystals. Broken Hill, Zambia also yields transparent crystals to 1 cm.

faceted smithsonite gems - Namibia

Smithsonite: Tsumeb, Namibia (8.00, 10.40). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Mexico produces material with much variation in color, including bi-colors, as well as pink and bluish crusts. The pink material from Mexico is especially lovely.

Laurium, Greece yields fine blue and green crystals.

The Masua and Monteponi mines in Sardinia, Italy once produced translucent, deep yellow, banded material. However, these mines are now closed.

faceted smithsonite - Sardinia

Under strong transmitted light, you could see the banding in this 6.17-ct yellow smithsonite. Pear mixed cut, 13.3 x 9.5 mm, Monteponi Mine, Iglesias, Sardinia. © The Gem Trader. Used with permission.

Other notable sources include the following locations:

  • United States: Marion County, Arkansas (yellow, banded crusts); California; Colorado; Georgia; Montana; Utah.
  • Algeria; Australia (yellow material); Austria; Belgium; China; France; Germany; Japan; Spain; Tunisia; United Kingdom.

Stone Sizes

Lapidaries can cut beautiful cabochons up to many inches from massive material from New Mexico, Sardinia, and other localities. Crusts in some localities are several inches thick. Facetable crystals are rare, and stones over 10 carats could be considered exceptional.

  • Private Collection: 45.1 (dark yellow, emerald-cut. Tsumeb, Namibia).

Care

You’re more likely to find smithsonites in a mineral collection than a jewelry collection. Reserve these gems for occasional wear or pieces with protective settings. For instance, pendants and earrings would make excellent jewelry choices. Store smithsonites separately from other harder, more common jewelry stones.

Since smithsonites are somewhat porous, don’t wear them while applying perfumes or other sprays. Avoid wearing them directly against your skin. Clean these gems only with a soft brush, mild detergent, and warm water, but don’t soak them. See our jewelry cleaning guide for more recommendations.

botryoidal smithsonite crystals - Namibia

Smithsonite, Berg Aukus, Namibia. Photo by Thomas Spann. Licensed under CC By 2.0.

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