mercury

Mercury is unlike any other metal. At room temperature, it is a shimmering liquid. In nature, mercury is found as a solid in the mineral cinnabar, as well as in natural compounds. This liquid metal is used in thermometers and electronics. Pure liquid mercury gives off toxic vapors. It also combines easily with other substances to form toxic compounds. Pollution from human activity releases mercury into the air, soil, and water.

Chemical symbol: Hg (from the Latin word "hydrargyrum," meaning liquid silver)
Properties: dense, shiny, silver-colored metal; liquid at room temperature
Toxicity: Gives off toxic vapors; combines with chemicals to form toxic compounds
Source: cinnabar ore
Used in: thermometers, barometers, batteries
Cool Fact: Its nickname, quicksilver, originally meant "living silver."

Image credits: main image, © istockphoto.com.