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The colors of rubies and emeralds are so striking that they define shades of red and green—ruby red and emerald green. But have you ever wondered how they get those colors?
Unlike the colorless aluminum ion, the chromium ion absorbs blue and green light when surrounded by the oxygen ions. The red light is reflected back, so that’s what you see in rubies.
Chromium is found in leather, cement, and other sources in the immediate household environment. ... However, concentrations of the chromate (VI) ion up to 450 ppm and of the chromate(III) ...