Emerald

Emerald is the green variety of beryl, colored by trace amounts of chromium and sometimes vanadium. Like alexandrite, emerald requires beryllium and chromium to occur together - an extremely unlikely geological event because these elements originate from different rock types.

Colombian emeralds formed through a unique process: beryllium-bearing hydrothermal fluids percolated through chromium-rich black shales during Cretaceous mountain building. The specific chemistry of these shales provided the chromium coloring agent, while the hydrothermal fluids supplied beryllium, silicon, and aluminum. The result is emeralds with a warm, pure green color unique to Colombian material.

Almost all emeralds contain visible inclusions - fractures, mineral crystals, and fluid-filled cavities called 'jardin' (French for garden) because of their resemblance to plant growth. Unlike most gemstones, these inclusions are accepted and even valued in emeralds. An eye-clean emerald is so rare that it would be suspected of being synthetic. The gemological trade accepts oil treatment of emeralds (filling surface-reaching fractures with cedar oil or resin) as standard practice.

Emerald is identified by its distinctive green color, hexagonal crystal habit, hardness of 7.5-8, and characteristic inclusions. The green is noticeably different from green tourmaline (more blue-green) or chrome diopside (too dark).

Distinguish from green tourmaline (different crystal system, different green tone), tsavorite garnet (no hexagonal crystals, different inclusions), and chrome diopside (softer, too dark). Emerald's inclusions under magnification are diagnostic - three-phase inclusions (containing solid, liquid, and gas) in Colombian emeralds are essentially fingerprints of natural origin.