Answer: color, cleavage, clarity, durability, and crystal system
Explanation: color - distinctly green color that ranges between bluish green and slightly yellowish green.
cleavage - one direction of imperfect cleavage
clarity - almost every natural emerald has eye-visible characteristics that can be inclusions, surface-reaching fractures, or healed fractures. Treatments to fill the fractures with oils, waxes, polymers, flux and other materials to reduce their visibility has been common practice for hundreds of years.
durability - emerald is very hard, but almost all specimens have inclusions and surface-reaching fractures that compromise their durability
crystal system - hexagonal