Emerald is the green gemstone variety of the mineral beryl (Be₃Al₂Si₆O₁₈). Its characteristic deep green color is caused by trace amounts of chromium and/or vanadium. With a hardness of 7.5–8 on the Mohs scale, emerald is relatively hard but often fragile due to natural inclusions and fractures. These internal characteristics—known in gemology as jardin (French for "garden")—are accepted as part of the natural beauty of emerald.

Emeralds are primarily classified based on origin, color intensity, transparency, and treatment:

1. Colombian emerald
   • The most sought-after variety. Intense green color, often slightly translucent with a characteristic “jardin”.
   • The Muzo and Chivor mines produce the finest quality emeralds.
2. Zambian emerald
   • Slightly darker green with a bluish undertone. Fewer inclusions and often clearer than Colombian stones.
   • Highly valued for its clarity and durability.
3. Brazilian emerald
   • Lighter shades of green, often with lower color intensity.
   • Suitable for larger gemstones at a more affordable price.
4. Synthetic emerald
   • Lab-grown and chemically identical to natural emerald.
   • Less valuable but visually attractive and virtually inclusion-free.

Emerald is mined around the world, with the main sources being:

• Colombia – by far the best-known and historically most important producer.
• Zambia – produces large quantities of emeralds with excellent clarity.
• Brazil – produces both natural and synthetic emeralds.
• Afghanistan, Ethiopia, Pakistan – smaller but high-quality deposits.
• Madagascar – an emerging source of commercially attractive emeralds.

Emeralds often contain natural fractures, making treatments common:

• Oil treatment (most common)
  • Inclusions and fractures are filled with colorless oil (usually cedarwood oil) to improve transparency.
  • Considered an acceptable treatment when properly disclosed.
• Resin or polymer treatment
  • More durable alternatives to oil. They may be colorless or tinted.
  • Treatment with green resin generally reduces the gemstone's value significantly.
• No treatment (very rare)
  • Untreated emeralds are exceptionally rare and highly valuable.
  • They require certification from a recognized gemstone laboratory.