Gemstones are assigned to the nine grahas, one each, and prescribed as a remedial measure when a graha is judged weak or afflicted:
| Graha | Stone | Graha | Stone |
|---|---|---|---|
| Sun | Ruby | Venus | Diamond |
| Moon | Pearl | Saturn | Blue sapphire |
| Mars | Red coral | Rahu | Hessonite |
| Mercury | Emerald | Ketu | Cat's eye |
| Jupiter | Yellow sapphire |
Together these are the navaratna, the nine gems, and they appear as a set in Indian jewellery independently of any astrological advice.
This is the most commercial part of Indian astrological practice, and the part where the conflict of interest is most direct: the same person who identifies the affliction very often sells the stone, at prices that scale with carat weight and claimed quality. A yellow sapphire recommendation is a purchase recommendation.
It is also the part most exposed to the Drugs and Magic Remedies (Objectionable Advertisements) Act, 1954. That statute defines a "magic remedy" to include a talisman, mantra or kavacha claimed to have effect on a disease or condition, and it prohibits advertising such claims. A gemstone advertised as acting on illness falls squarely inside it.
This site's position is stated once and applied everywhere: a gemstone is jewellery. We describe the tradition — which stone goes with which graha, and why the correspondences were drawn — and we make no claim that wearing one produces any physical, medical or financial effect. Nothing here is a substitute for professional advice. Before buying a stone on astrological grounds, apply the one test that always applies: does the person recommending it profit from supplying it?