Composition of Emeralds

An emerald bracelet

Emeralds are an opaque to transparent, crystalline, hard mineral (7.5 to 8 on the Mohs scale, on which a diamond is a 10) that are a member of the beryl family. Their crystal system is hexagonal. They are considered a precious gemstone, although they can be brittle because of flaws that developed when they formed.

Beryl Composition

Beryl is composed of aluminum, beryllium and silicate. The chemical formula is Al2Be3[Si6O18]. What makes an emerald different from a pure beryl is the chemical impurities that change its color.

Emerald Color Components

The color of emeralds can be green, blue-green, green-blue and yellow-green, but there are also blue-green varieties with shades in between. These colors are owing to small amounts of beryllium (Be), iron (Fe), vanadium (V), chromium (Cr) and aluminum silicate.

Physical Inclusions

Within emeralds there can be gas bubbles, fissures, small crystals and fluid, which are referred to as "jardin," the French word for garden. The number and size of inclusions determine how transparent or opaque an emerald is.

References

• Smithsonian Museum: Mackay Emerald Necklace
• Cochise College: Inclusions In Emeralds
• Mineral Miners: Emerald: Mineral Information Page
• University of Emporia: Varieties and Uses of Beryl: Emerald

Resources

• The Mineral and Gemstone Kingdom: Emerald