Cerussite: Gemstones Information
Cerussite is lead carbonate, PbCO3. It is usually white or grey in colour,but black, blue and green colours are known, these two latter owing their colour to copper; faceted cerussite is almost invariably transparent and colourless. The hardness is 3.5; it is notoriously brittle and heat-sensitive.The SG is in the range 6.46–6.57. The lustre is adamantine and the RIs are 1.804, 2.076 and 2.078. The birefringence is 0.274, biaxial negative.The luminescence is variable but under SWUV. It usually shows a pale blue or green glow. Some cerussite from Utah is said to show a bright orange under LW.Most facet-quality material comes from Tsumeb, Namibia. Despite difficulties in cutting, the dispersion of 0.055 makes the occasionally encountered gemstone quite spectacular. Collectors value the orthorhombic crystals which are frequently twinned to give pseudo-hexagonal shapes.