Lead, atomic number of 82, is very soft, blue-gray, metallic element and has been used since antiquity. Because it is so soft, lead is usually alloyed with other elements. Water pipes in ancient Rome, some of which still carry water, were made of lead. The English words plumber and plumbing are derived from the Latin word for lead, plumbum. Plumbum is also the source of the chemical symbol for lead, Pb.
Lead is a very heavy element. Native lead was found in Sweden, but it is rare to have the element alone in nature. Combined with other elements, it forms a variety of interesting and beautiful minerals, all of which are heavy due to their lead content. The most significant lead mineral is galena (PbS, lead sulfide). Galena deposits have been worked worldwide for their lead. During the Civil War, the Union Army made bullets from lead derived from a galena mine at Balmat, New York. Anglesite and cerussite ((PbSO4, lead sulfate and PbCO3, lead carbonate respectively) are two other lead-based minerals.
All major radioactive elements (such as uranium) break down and create lead as one of their end products. Interestingly, lead is used to safely store radioactive materials because it absorbs radiation from the radioactive isotopes.
Lead is toxic. It can cause damage to the digestive and nervous systems, so its use in some applications has been discontinued. Lead poisoning is monitored in children to prevent any permanent damage. At one time lead was added to gasoline to eliminate “knock” in car engines. It was also in paint, but the lead-based paints have a sweet taste, and some children were eating the paint and getting serious lead poisoning.
(Above left: Galena crystals on fluorite from Illinois. Above right: cerussite crystals from Morocco. Drawings used with permission. ©2000, 2001 Darryl Powell)
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