Mood rings first made their appearance in the 1970’s.  You wore it on your finger

and the color of the stone would reflect the state of your emotions.  There were

many incarnations of the personal mood-detector. There was a big flat

masculine-looking ring, a watch that changed color, pendants and even nail polish.
The way mood rings work is simple. The stone in a mood ring is either a hollow

glass shell filled with thermo tropic liquid crystals, or a clear glass stone

sitting on top of a thin sheet of liquid crystals. These liquid crystal molecules

are very sensitive and they change position according to changes in temperature.
This change in molecular structure affects the wavelengths of light that are

absorbed or reflected by the liquid crystals, resulting in an apparent change in

the color of the stone.
For example, as the temperature increases, the liquid crystal molecules twist

slightly in one direction. This twist causes the liquid crystal substance to

absorb more of the red and green portions of the visible light, and reflect the

blue part.  This causes the stone to appear dark blue.
When the temperature decreases, the molecules begin to twist in the other

direction, and reflect a different portion of the spectrum . . . which explains

why they were totally useless outdoors in winter when they would just turn gray

and stay like that
Below is a list of the various colors and their associated feelings:
Slate blue – Happiness, Love & Joy

Blue – Relaxed, At Ease and Calm

Blue/Green – Somewhat Relaxed

Green – Average reading – Not under stress

Yellow/Green – Troubled & Uneasy

Grey – Anxious/ Nervous

Black – Tense, Nervous, Anxious, Harassed

So…If you are having one of those days when you just don’t know what you’re

feeling, slip on a mood ring and it will tell you.