Lead
by
As heavy as lead—it's probably something you say all the time and,
if you've ever tried to lift a car
Photo: A sample of galena (lead sulfide), by far the most important lead ore. Photo by courtesy of US Geological Survey.
Where does lead come from?
“Lead poisoning is a classic example of what happens when we take a material that was once buried deep underground and with which humans rarely had contact and introduce it widely into humans' ecology.”
Gerald Markowitz and David Rosner, Lead Wars, 2014.
Lead is reasonably widespread (about the 36th most common element in Earth's rocky
crust) but, like most other
Photo: The Old Wheatly lead mine, near Phoenixville. Chester County, Pennsylvania. Photo by Geological Society of America courtesy of US Geological Survey.
Galena is turned into pure lead metal through a multi-stage process. First it is
crushed and washed to remove dirt and impurities. Then the lead is
extracted either by smelting (heating in a furnace with coke) or in a
two-stage process involving first roasting to convert lead sulfide into lead
oxide, then smelting to remove the oxygen. Other precious
metals are usually mixed in with the galena ore (including
Many countries mine lead, with leading producers including China (responsible for half of all mining), Australia, Peru, Mexico, and India. Although the United States once mined about a third of all the world's lead, by 2018 it was mining only around 7 percent. Most US mined lead comes from Alaska and Missouri, with the rest coming from Idaho and Washington. About 60 percent of lead used in the US is produced from "secondary" (recycled) sources.
Chart: Who produces the world's lead? About half of it comes from China. Chart shows world mine production for 2018. Source: US Geological Survey, Mineral Commodity Summaries, February 2019.
What is lead like?
Lead is a soft, heavy, blueish gray metal that lives in group 14 (formerly IVa) of the Periodic Table of chemical elements.
Physical properties
On the face of it, when it comes to metallic properties, lead doesn't put up much of a
showing. It's soft, weak, a poor conductor of
Chemical properties
Photo: Health and safety concerns mean lead is no longer so widely used in paints. Photo by Brian M. Brooks courtesy of US Navy.
Lead has a valency (combining power) of either +2 or +4, joining with a variety of
other elements to make useful lead (II) and lead (IV) compounds,
including oxides, sulfates, and carbonates. Industrially, the most
important lead compound is a yellow powder called litharge
(lead (II) oxide or lead monoxide), which is a vital ingredient in
all kinds of
What do we use lead for?
Photo: Much of the world's lead finds its way into vehicle (car and truck) batteries. In the United States, some 85 percent of all lead ends up in batteries like this. Around 116 million batteries like this were shipped in the United States during the first ten months of 2018 alone (a slight increase on the year before). [Source: US Geological Survey, Mineral Commodity Summaries, February 2019.]
Consider lead's useful properties and you can more or less predict what people will use it for:
- Protection: It's very dense and heavy, and that's why it's so useful as a material for screening people against harmful
radiation (
X ray technicians, known as radiographers, usually stand behind lead screens or wear lead aprons). - Coloring: Lead's brightly colored, highly durable compounds were a natural choice for pigments and dyes,
though health and safety concerns have seen lead removed from many
paints (especially those used on children's toys). - Plumbing: When people realized that lead resisted corrosion, they recognized it as an
excellent material for such things as roofing and water pipes.
(Again, health and safety concerns mean many lead water pipes have been
removed and replaced with apparently safer
plastics.) - Weaponry: Lead's weightiness made it useful in
bullets and shot though, once more, these uses are dwindling with concerns about health effects and pollution. - Batteries: Although lead doesn't conduct electricity well, it can be
used with sulfuric acid to store and release electrical energy
through chemical reactions—and that's how
car batteries work (the ones that kick-start cold car engines). With other uses of lead in rapid decline, batteries are now the biggest single use of lead. - Alloys: Important lead
alloys include pewter (used for making tableware), corrosion-resistant coverings for electrical cables, acid-resistant linings for chemical tanks, and solders with relatively low melting points. - Pencils? Nope! The "lead" in a pencil contains no lead metal (it's made from a form of
carbon called
graphite) but, in decades past, the paint that covers the wooden shaft sometimes used to contain lead. Modern pencils are covered with "unleaded" paint, so there should be no risk now to sucking on a pencil. There is much greater risk from such things as old lead water pipes, dust from old flaking paint, and lingering emissions from old vehicles still using leaded fuel.
