γαλήνη

Ancient Greek γαλήνη (galḗnē) meant calmness or tranquility, and the Roman naturalist Pliny the Elder applied the related form galena to the principal ore of lead. The name may reference the mineral's smooth, calm-looking cubic crystal faces—flat, reflective surfaces that gleam with a metallic luster that ancient observers found serene. Galena is lead sulfide (PbS), and it has been mined for at least five thousand years.

The ancient world depended on galena for lead, which was extracted by simple smelting. Romans used lead for water pipes (plumbum, giving us plumbing), cooking vessels, cosmetics, and wine sweetener (lead acetate, called sugar of lead). The consequences were catastrophic: chronic lead poisoning may have contributed to declining birth rates, neurological disease, and political instability in the late Roman Empire.

Galena found new significance in the early twentieth century as a semiconductor. Crystal radio sets, the first widely available consumer radios in the 1920s, used a thin wire (a cat's whisker) touching a galena crystal to detect radio signals. Before vacuum tubes and transistors, galena was the material that brought radio into homes.

The mineral remains the world's primary source of lead, mined in China, Australia, and the Americas. Lead-acid batteries, which power nearly every car on earth, depend on lead extracted from galena ore. A Greek word for tranquility names the raw material of a metal that has both built and poisoned civilizations for five millennia.