Domeykite cabochons. © 49erMinerals. Used with permission.
Bright, silvery metallic cabochons of algodonite and domeykite are attractive and unusual. Faceted pieces are rarely seen but very beautiful when polished to a high luster.
Domeykite cabochons. © 49erMinerals. Used with permission.
Bright, silvery metallic cabochons of algodonite and domeykite are attractive and unusual. Faceted pieces are rarely seen but very beautiful when polished to a high luster.
| Data | Value |
|---|---|
| Name | Algodonite |
| Crystallography | Hexagonal crystals rare; usually massive, granular, reniforn. Domeykite is isometric. |
| Colors | Silver white to steel gray; tarnishes rapidly to a dull brown. |
| Luster | Metallic. |
| Hardness | 3-4 (Domeykite: 3-3.5). |
| Fracture | Fracture uneven in domeykite, Subconchoidal in algodonite |
| Specific Gravity | 8.38 (Domeykite: 7.92-8.10). |
| Cleavage | None |
| Transparency | Opaque. |
| Formula | Cu6As (Domeykite = Cu3As). |
| Etymology | Algodonite, after Los Algodones Mine, Coquimbo, Chile. Domeykite, after the Polish mineralogist Ignacy Domeyko. Mohawkite, after the Mohawk Mine, Keweenaw Co., Michigan. |
| Occurrence | Localities that produce copper arsenide minerals. |
| Birefringence | None |
Algodonite: Mohawk Mine, Keweenaw Peninsula, Michigan (each – 1 inch across). Photo © Joel E. Arem, PhD, FGA. Used with permission.
Algodonite and domeykite are both copper arsenides. However, algodonite forms in the hexagonal crystal system while domeykite forms in the isometric system. Both can occur mixed together as well as with other minerals.
Mohawkite — a mixture of algodonite, domeykite, copper, silver, and other minerals — also yields very striking cabochons.
“Story in History,” mohawkite, silver, and bronze pendant. © Lauren Tripp, photo and jewelry, Brighter Shade of Blue. Used with permission.
With a specific gravity (SG) of 8.38, algodonite is one of the densest gemstones used as jewelry. (Domeykites range from 7.92 to 8.10). This property usually easily distinguishes it from gems of similar appearance. However, a few gem materials have SG ranges and colors that approximate algodonite’s.
Bismutotantalite and stolzite are very rarely encountered in cut forms. They also lack algodonite’s metallic luster. Natural cinnabar is rarely cut and usually, but not always, has a bright red color. (Be aware that some so-called “cinnabar” jewelry may just be red lacquer-coated wood, which is much lighter than actual cinnabar as well as algodonite).
Niccolite (nickel arsenide) comes close to algodonite in colors and luster and also makes beautiful cabochons. However, it has a somewhat lower SG (7.78).
Scientists have synthesized algodonites and domeykites in crystal form for research purposes. However, there’s no known jewelry use for this lab-created material.
Algodonites tarnish rather quickly. Their surfaces turn a drab brown and lose their metallic luster. To prevent this, they must be sprayed with lacquer.
Naturally tarnished algodonite mass, 3.2 x 2.7 cm, Mohawk Mine, Mohawk, Keweenaw County, Michigan, USA. Photo by John Sobolewski. Licensed under CC By 3.0.
As fine crystals, algodonites occur in Painsdale, Michigan. As masses, they occur in Chile at Los Algodones Mine, Coquimbo and Cerro de Los Aeguas, Rancagua.
Domeykite occurs in the following locations:
Related minerals are found at Beloves, Czech Republic and Mesanki, Iran.
Mohawkite occurs only in the Mohawk Mine, Keweenaw Peninsula, Michigan.
Mohawkite, 4.6 x 3.1 x 2.5 cm, Mohawk Mine, Mohawk, Keweenaw Co., Michigan, USA. © Rob Lavinsky, www.iRocks.com. Used with permission.
Lapidaries could cut these copper arsenide materials into cabochons of almost any size, depending on the availability of large masses of rough with metallic luster.
Algodonites, domeykites, and mohawkites are heat sensitive. Lapidaries should take care when cutting these materials.
Of course, copper arsenides contain copper and arsenic, and both pose health risks. Therefore, gem cutters should take precautions when working with these materials. Consult our lapidary safety guide and tips for handling toxic gem materials for more information.
Wearing finished algodonites and other copper arsenides as jewelry should pose no health risks. Since these materials are somewhat soft (hardness 3-4), pendants and earrings make good jewelry options. Rings would require protective settings.
For cleaning recommendations, consult our gemstone jewelry care guide.
Domeykite cabochons. © 49erMinerals. Used with permission.
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