In India, navratna jewellery is set with the Navagraha which literally translates to the nine precious stones representing the nine planets of the Hindu astrological system and their associated deities.
These stones are worn individually or all together in a jewel called the navratna believed to negate danger and to attract beneficial influences and energy.
For further reading see O. Untracht, Traditional Jewelry of India, Thames and Hudson,London, 1997, page 304