CERRUSITE: Tsumeb, Namibia (32.87). Photo © Joel E. Arem, PhD, FGA. Used with permission.
Cut cerussite is as beautiful as diamond since has higher dispersion, is usually free of any body color, and has an adamantine luster. However, cerussite is extremely soft and one of the most brittle and heat sensitive of all minerals. Cutting a gem is a major chore, and cutting a very large one without breaking it is almost impossible.
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| Faceted | 5 carats plus |
| to /ct |
| Data | Value |
|---|---|
| Name | Cerussite |
| Colors | Colorless, white, gray, “smoky” greenish (Cu inclusions), yellowish. Dark gray or black material is due to inclusions. |
| Crystallography | Orthorhombic. Crystals common, elongated tabular, often twinned and striated; acicular, massve. |
| Refractive Index | 1.804-2.079 |
| Luster | Adamantine to submetallic; vitreous; resinous; pearly |
| Hardness | 3 - 3.5 |
| Wearability | Display Only |
| Fracture | Conchoidal |
| Specific Gravity | 6.55 |
| Birefringence | 0.275 |
| Cleavage | Distinct 1 direction |
| Dispersion | 0.055 (greater than diamond). |
| Stone Sizes | Large masses of transparent rough are known from Tsumeb, Namibia, that could cut stones of several thousand carats. The real problem is cohesion of large stones. Catseyes are known from 2-6 carats; the material is from Tiger, Arizona, and Tsumeb, Namibia. Smithsonian Institution (Washington, D.C): 4.7 (pale yellow, Tsumeb, Namibia); 109.9 (smoky Tsumeb, Namibia) National Museums of Canada (Ottawa, Ontario): 71.25 (colorless octagon, Tsumeb, Namibia) Private Collection: 408 (brownish-gray oval, Tsumeb, Namibia); 262 (emerald cut, colorless, Tsumeb, Namibia) |
| Luminescence | Pinkish orange (Utah) or yellow shades in LW. Pale blue or shades of green in SW. |
| Luminescence Present | Yes |
| Luminescence Type | Fluorescent, UV-Long, UV-Short |
| Transparency | Transparent to opaque |
| Absorption Spectrum | Not diagnostic. |
| Phenomena | Chatoyancy. |
| Formula |
PbCO3 |
| Pleochroism |
None. |
| Optics |
a = 1.804; β = 2.076; γ = 2.079. Biaxial (-), 2V = 9°. |
| Optic Sign | Biaxial - |
OPTICS: a = 1.804; β = 2.076; γ = 2.079. Biaxial (-), 2V = 9°
OCCURRENCE: Secondary mineral in the oxidized zones of lead deposits. Many localities known:
Tiger Arizona; Colorado; Idaho; South Dakota; Utah; New Mexico; Montana; Nevada; California
Broken Hill Mine, Zambia; Dundas, Tasmania; Broken Hill, N.S.W., Australia; Monte Poni, Sardinia; Leadhills, Scotland.
Tsumeb, Namibia: source of the largest and finest gem material; colorless, gray and yellowish, in masses up to several pounds (completely transparent)
COMMENTS: Cut cerussite is as beautiful as diamond since has higher dispersion, is usually free of any body color, and has an adamantine luster. However, cerussite is extremely soft and one of the most brittle and heat sensitive of all minerals. Cutting a gem is a major chore, and cutting a very large one without breaking it is almost impossible. Consequently, faceted cerussite is one of the rarest of all gems. Abundant rough material is available among the thousands of crystals and crystal fragments recovered from Tsumeb, Namibia. Few cutters, however, have the skill and knowledge required to successfully fashion a gem from this rough. The cost of a cut stone will therefore largely reflect the cutting cost. Time, patience skill, and tender loving care are essential.
NAME: From the Latin cerussa, the name of an artificial lead carbonate.
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