Mercury is found all over the world as an ore in combination with cinnabar. It tends to be found in high concentrations in geographic regions where there are hot springs or volcanos. China and Kyrgyzstan are the modern global leaders in mercury production, but mercury has been known, produced and used since ancient times. Trace amounts of mercury also occur naturally in fish and other seafood. Sometimes, this can become toxic.

China produced two-thirds of the world's mercury in 2005 and Kyrgyzstan produced the second largest amount. Mercury has been known since ancient times and was discovered in Huancavelica, Peru, in 1563. Some of the world's mercury mines, like the ones in the United States, Mexico, and Italy have been significantly depleted. Mercury is usually found in cinnabar, corderoite and livingstonite in its harmless, inert form. Soluble mercury, which is toxic, is obtained by subjecting these ores to a reduction process.

Mercury is a liquid metal element that has many common uses in industry and medicine. The scientific symbol for mercury is Hg. This comes from the Greek word for the element, hydrargyum, which means watery silver. Mercury is a metal that a liquid at room temperature.

Mercury melts at negative 37.89 degrees Fahrenheit and boils at 674.11 degrees Fahrenheit so on Earth, in its pure form, mercury is a liquid metal. Because mercury expands or contracts evenly when it is subjected to changes in temperature and pressure, it makes an accurate tool for measuring both. It is a frequent ingredient in both thermometers and barometers for this reason.

Mercury is so highly reflective that it was once used to float the Fresnel lenses that enhanced the visibility of the lights in lighthouses. The astronomers at the Large Zenith Telescope Project use a huge rotating mercury mirror to observe the night sky. Dental amalgams, florescent light bulbs and dry cell batteries also include mercury.

High levels of mercury are found in some fish. Symptoms of mercury poisoning can include tremors and impaired cognitive skills, and were first observed in people who used mercury to process animal skins to make hats. People who have mercury poisoning may need to have their dental fillings replaced. Mercury is also found as an ingredient in mascara. Even though the potential for mercury poisoning is well known, it has only been outlawed for cosmetic use in one state, Minnesota, as of 2008.