The Legend of Vala
In ancient times there lived a demon named Vala. Vala conquered the god Indra and his celestials, and reigned supreme and invincible in the universe. The gods, on the occasion of a religious sacrifice, jocularly asked him to play the part of the sacrificial animal. Vala consented to play the role as the sacrificial animal and pledged his word to be bound at the sacrificial stake. Whereupon the gods turned the jest into earnest and killed the invincible Vala in the mockery of a religious sacrifice. Thus Vala yielded up his ghost for the good of the universe and for the welfare of the gods. The severed limbs and member of his sanctified body, were converted into the seeds of gems.
The Gods, the Yakshas, the Siddhas and the Nagas eagerly rushed to collect those seeds of gems. The Gods came riding in their aerial cars, and carried away the seeds of gems for the own use, some of which dropped down on Earth through the violent concussion of the air. Wherever they dropped - whether in oceans, rivers, mountains or wildernesses - the places became the origins of mines through the celestial potency of their respective seeds.
Drops of his blood became rubies, his skin, yellow sapphires, his eyes, blue sapphires and his bones shattered and became diamonds. Vala's teeth fell into the oceans and landed on oysters where they became pearls. His intestines were also thrown into the sea and became coral. His ruddy fingernails changed to hessonite garnets. His toenails became the seeds red pyrope garnet. Vala's bright green bile became emeralds. His fat turned into jade while his semen became quartz. The rosiness in his complexion became bloodstones. Finally even Vala's last war cry that echoed around the heavens as he was killed was transformed into cat's eye. It is said that the "chandrakanta," or moonstone, was formed from the gleam of Vala's eyes.
The name Vala conveniently translates to "soul of the cave." Vala is also the source word for "valley." Strangely enough, caves and valleys are often the origin of gems. Thus in all, there are eighty four different parts and constituents of the demon Vala. Of them, only twenty-one are described as gems or jewels due to peculiar brilliance they possess. Of these twenty-one gems, only nine are most famous for their radiance & special powers and are hence known as Navaratna.