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.
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.
Identifying Characteristics
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.
Comparison of Selected Physical and Optical Properties of Anglesite, Cerussite, and Phosgenite
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.
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!