Gem Minerals
Beryl
What it is
One mineral, many gems. Beryl is beryllium aluminum silicate that produces entirely different gemstones depending on trace impurities: chromium makes emerald green, iron makes aquamarine blue, manganese makes morganite pink, and iron in a different oxidation state makes heliodor yellow.
How it forms
Crystallizes in granite pegmatites — the last, most element-rich fluids of a cooling magma body. Pegmatites cool slowly deep in the crust, allowing crystals to grow to remarkable sizes. Some beryl crystals exceed several meters.
Be₃Al₂Si₆O₁₈ (Hexagonal)
