mica

Latin mica meant a crumb, a morsel, a grain. The word was applied to a group of silicate minerals that split into extraordinarily thin, flexible, transparent sheets—so thin they crumble at the edges like bread. The name stuck because the mineral's behavior matched the word perfectly: mica flakes into tiny pieces, glittering crumbs that catch light.

Before glass was widely available, mica served as window material. Muscovite mica, mined near Moscow (hence the name, from Muscovy glass), was split into thin sheets and used for window panes in medieval Russia. The material was called isinglass—a corruption of the German Hausenblase, though the mica use predated the fish bladder association. Through a mica window, the world looked slightly golden.

Mica's electrical insulating properties made it essential to the electronics industry. From the 1890s through the mid-twentieth century, mica was used as an insulator in vacuum tubes, capacitors, and electrical equipment. India's Bihar region was the world's largest mica producer, and the mines employed—and continue to employ—child laborers in conditions that have drawn international condemnation.

The glitter in cosmetics, paint, and children's craft supplies is almost always mica. Ground to a fine powder, mica produces the sparkle in eyeshadow, nail polish, car paint, and Christmas ornaments. A Latin word for crumb now glitters on millions of faces and surfaces around the world, its tiny fragments catching light exactly as they did when Roman naturalists first noticed them.