The mood ring was one of the biggest fashion fads of the 1970s. Marketed as an accessory for the "Me Decade," a time when people began to actively explore their feelings, the color-changing jewelry first became popular in New York City and quickly spread throughout the United States. Each mood ring contained a temperature-sensitive liquid crystal encased in quartz. As the body temperature of the wearer changed, the crystals changed colors. Each color the ring displayed supposedly corresponded to a different mood. There were seven colors in all, each with a different meaning: blue meant happy; reddish brown meant insecure; black meant the wearer was upset; golden yellow was a sign of tension; and so on. From a scientific perspective the mood ring did have some validity as an indicator of someone's emotional state; the metal band of a mood ring conducted heat from the finger to the liquid crystal, which changed color in response to the temperature of the skin.
The mood ring was invented in 1975 by Joshua Reynolds, a thirty-three-year-old marketing executive from New York City who took an incredibly simple product idea and turned it into a national craze. After making a fortune off the mood ring, Reynolds later went on to invent the Thigh Master exercise machine.
Like all fads the mood ring had a very limited life span. In this case the life span of the product was quite literally fixed, in that the heat-sensitive crystals would only emit their color changes for a period of two years before they would settle permanently into a shade of black. By 1977, just two years after their introduction, the rings had faded in popularity.
Long, Mark A. Bad Fads. Toronto, Canada: ECW Press, 2002.