A Jyotish gem is a gemstone prescribed under the Vedic astrological system, called Jyotish, to strengthen or balance one of the navagraha, the nine planetary influences that the system holds to govern human affairs. The Jyotish prescription tradition is one of the oldest continuous gemmological practices in the world and remains commercially important in India, Sri Lanka, Nepal and the South Asian diaspora.

The Navaratna correspondences

The Navaratna, literally the nine gems, is the canonical Jyotish grouping. The correspondences are: ruby for the Sun, pearl for the Moon, red coral for Mars, emerald for Mercury, yellow sapphire for Jupiter, diamond for Venus, blue sapphire for Saturn, hessonite garnet for Rahu, and chrysoberyl cat's-eye for Ketu. A Jyotish prescription typically nominates one or more stones, sometimes the full Navaratna set, on the basis of the wearer's natal chart.

Prescription criteria

A serious Jyotish prescription specifies the stone, the minimum carat weight in ratti, the metal of the setting, the finger or position to be worn, the day of activation and the appropriate prayer. Stones are required to be natural, ideally unheated, and free of significant inclusions or visible defects in the prescribed body colour. Synthetic, treated and assembled stones are not generally accepted. Where the primary stone is unaffordable, traditional substitutes called uparatna are accepted, although they are regarded as less effective.

Trade significance

Jyotish prescription is the underlying driver of a significant fraction of demand for unheated Sri Lankan sapphire, Burmese ruby, Colombian emerald, natural pearl, hessonite garnet from Sri Lanka and Tanzania, and chrysoberyl cat's-eye from Sri Lanka and India. Many Indian retailers including Tanishq, Gem Selections and Gemstoneuniverse maintain dedicated Jyotish or Navaratna ranges, and gemmological laboratories in India, including the Gemological Institute of India and IIGJ, issue certificates oriented to Jyotish use.