As beautiful as a diamond, a faceted cerussite actually has higher dispersion and usually excellent transparency, colorless or light body color, and an adamantine luster. However, this gem is notoriously difficult to cut and too soft for jewelry use.
Although there’s an abundance of cerussite rough available, few faceters have the knowledge and ability to successfully fashion a gem from this material. Cutting cerussite is a major chore, and cutting a large one without breaking it is almost impossible. Time, patience, skill, and tender loving care are essential. Consequently, faceted cerussites number among the rarest of gems. The price of a cut stone will largely reflect the cutting cost and the size of the gem.
An important lead ore, cerussite belongs to the aragonite mineral group, which includes aragonite, strontianite, and witherite. Like its fellow group members, cerussite is a collector’s gemstone. Its hardness of 3-3.5, very brittle tenacity, and distinct cleavage make it difficult to cut and risky to wear as jewelry. In addition, it has exceptional heat sensitivity.
About cerussite’s extreme sensitivity to thermal shock, Joel Arem writes: “This property became painfully evident when a 300+ carat, flawless, emerald-cut cerussite I was having cut finished out as a perfect gem — and instantly developed a thin, vertical cleavage crack across the middle of the entire stone, just because of the temperature change of removing the gem from the dop!” Cerussite, 10.62 cts, Tsumeb, Namibia. ? Joel E. Arem, PhD, FGA. Used with permission.
While faceted cerussites can make beautiful rarities, natural crystals can also make stunning specimens. They typically form in prismatic and tabular structures as well as intergrown twinned?shapes, such as hearts. “Snowflakes” — masses of delicate, reticulated, thin crystals — are highly prized. Cerussites can occur in many other unusual, visually interesting shapes as well.
Very rarely, cabbed cerussites may show a chatoyant “cat’s eye” effect.
Medium yellow-green cerussite cat’s eye, 3.19 cts, 6.4 x 4 mm, oval cabochon. (Unknown origin, possibly Namibia). ? The Gem Trader. Used with permission.
What is Chrome Cerussite?
Yellow and green cerussites are sometimes called “chromian” or “chrome cerussites” because their color is due supposedly to the presence of chromium (Cr). However, research has shown that Cr is likely not the exclusive cause of these colors. Other contributing factors may include natural irradiation, organic staining, and inclusions.
Cerussites may fluoresce pale blue or green in shortwave ultraviolet light (UV) and pinkish orange or yellow shades in longwave UV.
This crystal specimen features a cerussite on a plate of calcites. Under UV light, the cerussite fluoresces blue and the calcite orange. 8.0 x 7.0 x 4.0 cm (cerussite 3 cm), Tsumeb Mine, Tsumeb, Otjikoto Region, Namibia.? ? Rob Lavinsky, www.iRocks.com. Used with permission.
Cerussite’s combination of high dispersion, high specific gravity (SG), low hardness, and colorless to light colors will usually distinguish it from other more commonly faceted gemstones. However, two other rarely faceted collector’s gemstones have a comparable range of colors, hardness, and SG, as well as “over the limit” (OTL) refractive indices. Like cerussite, anglesite and phosgenite can be colorless as well as white, grayish, yellowish, or greenish. Their fluorescence under ultraviolet light (UV) can also appear yellowish. (Furthermore, these minerals can crystallize in close association).
Comparison of Selected Physical and Optical Properties of Anglesite, Cerussite, and Phosgenite
Fluorescence in UV
a = 1.877; b = 1.883; γ = 1.894
Can be yellow in LW. Pale blue/green in SW.
a = 1.804; b = 2.076; γ = 2.079
o = 2.114-2.118; e = 2.140-2.145
An?optic character reading can help distinguish cerussites from these other gems, and cerussite’s dispersion exceeds theirs as well.
This anglesite specimen is a pseudomorph after cerussite. Although the specimen has kept the external complex crystal structure of a cerussite, its chemical formula has become that of anglesite. 7.0 x 6.0 x 3.5 cm, Central Mine, Broken Hill, New South Wales, Australia. ? Rob Lavinsky, www.iRocks.com. Used with permission.
Cerussite, 32.87 cts, Tsumeb, Namibia. Photo ? Joel E. Arem, PhD, FGA. Used with permission.
Many localities produce cerussite, but the principal source of gem-quality material is Tsumeb, Namibia,?which yields?colorless, gray, and yellowish crystals, completely transparent, in masses up to several pounds.
The Touissit Mine near Oujda, Morocco?is another important source of cerussite gemstones.
Pear-cut cerussite, 120.22 cts. ? Joel E. Arem, PhD, FGA. Used with permission.
As if the physical properties of cerussite weren’t challenging enough, gem cutters should take precautions when working with cerussite since it contains lead. Wearing a respirator can prevent accidental ingestion or inhalation of dust particles. Using gloves or a glovebox will make cleanup much easier and safer. For more information on lead hazards and safety precautions, consult our article on toxic gems and safety tips.
Cerussite jewelry use isn’t advisable. It’s simply too fragile for anything except (very) occasional wear.
Faceted cerussites, 4.1 and 5.3 cts, Tsumeb, Namibia. ? Joel E. Arem, PhD, FGA. Used with permission.
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