Everyday Uses of Rocks and Minerals - Shelf 10
This shelf features mercury and lead, two important dense metals. Mercury is the only metal that is liquid at room temperature, which is why it has been used for so long in thermometers. As the metal expands and contracts in response to the temperature, it moves up and down the thin tube, and allowing the temperature to be read. Elemental mercury is poisonous, producing mental and coordination problems, so people have moved away from mercury thermometers and other everyday uses. Mercury is not found as a pure element in nature. It is mined from mercury ores, such as cinnabar (also called vermilion). Cinnabar is composed of mercury and sulfur and has been used as a red pigment since ancient times.
Lead is a very dense, very soft metal and has a low melting point, which allows it to be easily formed. Its density and easy of forming have made it the most common metal for bullets since the origin of firearms. It has also been used for fishing weights, as illustrated here. Its density is so great that it is used as a radiation shield. We most often see it in dentists' offices in the lead apron we wear to protect us from X-rays, but it is also used to shield nuclear reactors because it can capture any stray radiation before it enters the environment. Lead is, like mercury, poisonous, so it is beginning to fall out of everyday use. Its most common use today is in the lead-acid batteries found in automobiles. Lead is found in nature most often as galena, a compound with sulfur.