This Portuguese-cut, rich, lemon-yellow anglesite was custom cut by Spectrum Award winner Mark Kaufman. 62.27 cts, 24.0 x 17.0 x 11.0 mm, Touissit, Oujda-Angad Province, Oriental Region, Morocco. © Rob Lavinsky, www.iRocks.com. Used with permission.
Although anglesites with pale colors can show great dispersion and brightness, they’re difficult to cut and inadvisable to wear. Faceted pieces are true rarities, seldom seen except in very complete gem collections.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
| Data | Value |
|---|---|
| Name | Anglesite |
| Crystallography | Orthorhombic. Crystals usually tabular, prismatic; granular; massive; stalactitic. |
| Refractive Index | 1.877-1.894 |
| Colors | Colorless, white, yellowish gray, lemon to golden yellow, brownish orange, pale green, and blueish shades. |
| Luster | Adamantine to vitreous. |
| Hardness | 2.5-3 |
| Wearability | Poor |
| Fracture | Conchoidal |
| Specific Gravity | 6.30-6.39; usually 6.38. |
| Birefringence | 0.017 |
| Cleavage | Good 1 direction |
| Dispersion | 0.044 |
| Heat Sensitivity | Yes. |
| Luminescence | Weak yellowish fluorescence in SW and LW. |
| Luminescence Present | Yes |
| Luminescence Type | Fluorescent, UV-Long, UV-Short |
| Enhancements | Bleaching. |
| Transparency | Transparent to opaque. |
| Absorption Spectrum | Not diagnostic. |
| Formula | PbSO4 |
| Pleochroism |
None. |
| Optics | α = 1.877; β = 1.883; γ = 1.894. Biaxial (+), 2V ~ 75°. |
| Optic Sign | Biaxial + |
| Etymology | Named after the type locality, the Isle of Anglesey, Wales, UK. |
| Occurrence | Secondary mineral in lead deposits, formed by oxidation of galena (PbS). |
Anglesite: Tsumeb, Namibia (16.1, 16.2). Photo © Joel E. Arem, PhD, FGA. Used with permission.
Anglesite’s fire or dispersion equals that of diamond (0.044). If properly faceted, this gem can also show magnificent brilliance. However, due to its hardness of 2.5 to 3 and good cleavage, cutting requires great care.
Where anglesite occurs massively, it serves as a lead ore.
Anglesite’s specific gravity (SG) of 6.30 to 6.39 places it among the densest gem materials. Testing for SG can usually distinguish it from gems of similar appearance. However, two other rarely faceted collector’s gemstones have a comparable range of colors, hardness, and SG. Like anglesite, cerussite and phosgenite can be colorless as well as white, grayish, yellowish, or greenish. Their fluorescence under ultraviolet light (UV) can also appear yellowish.
| Hardness | SG | Fluorescence in UV | Refractive Index | Optic Character | |
| Anglesite | 2.5-3 | 6.30-6.39 | Weak yellowish. | a = 1.877; b = 1.883; γ = 1.894 | Biaxial (+) |
| Cerussite | 3-3.5 | 6.55 | Can be yellow in LW. Pale blue/green in SW. | a = 1.804; b = 2.076; γ = 2.079 | Biaxial (-) |
| Phosgenite | 2-3 | 6.13 | Strong yellowish. | o = 2.114-2.118; e = 2.140-2.145 | Uniaxial (+) |
A refractive index and an optic character reading with a refractometer and/or polariscope may be the most effective way to distinguish these gems. However, keep in mind that phosgenite may be anomalously biaxial. Some greenish phosgenites may show weak pleochroism, while anglesite has none.
“Cut Anglesites,” Minas Gerais, Brazil. Gem cutting by Afonso Marques. Photo by Eurico Zimbres. Licensed under CC By-SA 3.0.
Laboratories have synthesized anglesite crystals for geological research. However, there is no known use of this material for jewelry purposes.
In the early 1980s, amber-red anglesites from Touissit, Morocco were found to be the result of bleaching colorless and pale yellow crystal specimens. This treatment produced surface-deep colors. Only immersion in a bromide-water solution could reverse this coloration.
Rob Lavinsky first suspected this canary yellow to colorless anglesite from the late 1970s/early 1980s finds at Touissit to be a bleached specimen. (This treatment also produced orangey yellow colors). However, the colors of this crystal go through to the core, unlike those of surface treated material. These colors are, indeed, natural. 2.1 x 1.3 x 0.4 cm, Touissit, Oujda-Angad Province, Oriental Region, Morocco. © Rob Lavinsky, www.iRocks.com. Used with permission.
Although many localities across the globe can potentially yield gemmy crystals, only a few produce colorless and pale brown specimens.
Touissit, Morocco produces gem crystals in immense sizes for this species.
Tsumeb, Namibia produces large transparent yellowish crystals and, sometimes, gemmy colorless specimens.
Other notable gem-quality sources include:
“Anglesite,” 4.1 x 3.6 x 2.8 cm, Erupcion Mine, Villa Ahumada, Chihuahua, Mexico. © Rob Lavinsky, www.iRocks.com. Used with permission.
Faceted anglesites typically range from 1 to 6 carats. Very rarely does this material occur large enough to cut anything bigger than this. However, some rough, notably from Namibia and Morocco, has yielded 100+ carat gems. One such stone from Tsumeb, at 300 carats, broke during cutting!
Anglesites contain lead. When cutting this material, avoid ingesting or inhaling particles and wash your hands.
Jewelry use is not recommended.
Anglesite: Morocco (6.99). Photo © Joel E. Arem, PhD, FGA. Used with permission.
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