Lead

This dull, blue-grey material is a sample of lead, a metal so soft that you can see the dents in it where it has been dropped on the floor. As you will feel when you pick it up, this metal is incredibly heavy; as a result it is often used as ballast in boats and in belts to weigh down scuba divers. It is the densest metal after gold: this makes it exceptionally effective in sound barriers and as a shield against radiation – it is used in the aprons worn by dentists when they X-ray your teeth.

Lead is bright silver when freshly cut, but it very quickly reacts with air to form its distinctive dull lead oxide layer. This layer of lead oxide does not react with water, so it has traditionally been used in plumbing, roofing and outdoor paints.

However, lead is also extremely toxic to human health if inhaled or digested at high exposure levels, as it accumulates in the soft tissue and bones, damaging the nervous system and interfering with red blood cell production. In fact, its toxic effects have been observed since the Roman period. For that reason, although it has been useful to society for at least 8000 years, many of lead’s former uses have been discontinued or controlled. For example, lead was once used in face-whitening cosmetic preparations used by Japanese geisha and Elizabethans, in kohl eyeliner used by the Egyptians, and as a food and drink preservative in ancient Rome. In more recent years it has been removed from the majority of paints, leaded fuels and shotgun pellets.

Metallic lead doesn’t often occur on its own in nature, but can be found in ores with zinc, silver and copper. The main minerals in which is found are galena, cerussite and anglesite.