The colors of rubies and emeralds are so striking that they define shades of red and green—ruby red and emerald green. But ...

Rubies are formed of a mineral called corundum, comprised of aluminum oxide. The red color is caused by traces of chromium. Corundum also forms sapphire in many colors, which generally come from ...

Both rubies and emeralds are minerals, which is a type of rock with a consistent chemical composition and a highly ordered ...

One feature of compounds made with transition metals is their intense colour. There are many examples in nature, including ...

The deep blue hue that sapphires are known for comes from titanium and iron tinting the corundum, for example. Iron on its own makes yellow sapphires, and can also give us green stones.