Should I wear a gemstone for a weak planet?

only after a careful reading of the whole chart — and usually for a helpful planet, not a harmful one; prayer and conduct come first.

Each graha has a traditional gem: 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 (gomed) for Rāhu and cat's eye for Ketu. A gem is believed to strengthen its planet — which is why it should not be worn for a planet that rules difficult houses in your chart, since strengthening it may strengthen the problem.

A careful astrologer looks at the lagna, house lordships and daśā before suggesting a gem, and often prefers mantra and dāna first. Blue sapphire and cat's eye in particular are traditionally given only after a trial period.

If you are advised a gem, buy a natural, certified stone from a reputable seller at a sensible price, and remember that no stone replaces effort, medical care or good choices.

Source: Bṛhat Saṁhitā (chapters on gems); modern practice · Never for a harmful house lord

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