The bile of the great demon Vala was taken by the serpent king, Vasuki who split the heavens in two with one sweep of his mighty tail. With hood bedecked with jewels, his long body appeared like a bridge across the expanse of the heavens.
At that time, Garuda, the eagle-king carrier of the Supreme Lord Vishnu and the sworn enemy of serpents, came flying through the heavens and blocked Vasuki with his mighty claws. Upon seeing Garuda, Vasuki became so afraid that the he dropped Vala's bile to the earth near the beautiful forests and perfumed trees of Mt. Manikya. (Since the mountain ranges of South Africa and South America are the world's foremost producers of emeralds, one explanation would be that Mount Manikya consisted of the combined areas of these two continents prior to their separating.) It also descended upon the landlocked areas beyond the Himalayas. (Most probably present day Afghanistan and Pakistan).
This bile transformed into the seeds of emeralds, and wherever it fell there originated mines of emeralds. Seeing this, Garuda picked up some of these emerald-seeds, but their power was so great that even he was overcome with a fainting spell causing him to scatter small quantities in several areas.
The finest colors of emeralds are compared to the following elements in nature: the green color on the neck of a parrot; the color of a flower called in Sanskrit Shirisha; a blade of green grass; the color of fresh moss; the green found in a peacock's feather; the green on the back of a fire-fly. Anyone possessing fine quality emerald of any of these shades of green is blessed with great good fortune.
Most of the areas where Vala's bile fell, although exceptionally lush and beautiful, and rugged and hardly accessible. But the fine emeralds of these areas possess mystical powers, even to neutralize the poison of a king cobra.
Ancient Indian gemologists have given the highest praise to emerald possessing the following qualities: display a rich, even color; emit a soft glow; appear to glisten with gold dust inside; devoid of any serious internal or external blemishes. the gem also should be properly cut so that maximum light is refracted to the eye of one viewing it face up.
The emerald of superlative quality shines like green lightning and brings joy at first sight. Of second quality is one colored grass green, flawless, but with lighter tone and appearing transparent in the center (windowed). Dark colored emeralds showing little glow or fire should be considered inferior to those before mentioned.
Emeralds considered inauspicious are blackish, devoid of luster, appearing dirty inside or dried and brittle. Anyone concerned with their own well-being should never purchase or wear any oiled, dyed, or treated emerald. Also, emeralds of mixed colors are strictly forbidden.
Emeralds which are too light green are not considered true emeralds, but are called green beryl.
Emerald substitutes can be detected by differences in specific gravity and refractive index. Simply by sight and touch experienced gemologists can discern these differences.
Emeralds should be mounted in yellow gold, and worn, both by the doctor and patient, during the treatment of any disease, especially those caused by poison or an imbalance of the body's vital airs.
Top quality emeralds are deemed more valuable than a ruby of equal quality, while low quality emeralds are less valuable than comparable rubies. --- Sri Garuda Puranam: Chap. 71