Peridot, the August birthstone and stone for the 16th year of marriage, has a luscious green hue that has been valued since the time of the ancient Egyptians. Peridot gemstones are known for their solid, unchanging color, even in artificial light. The green of peridot is so constant because the color comes not from impurities, but from the gem itself being an iron magnesium silicate. In metaphysical beliefs, peridot is a stone of compassion, bringing good health, balancing emotions and promoting restful sleep.