Which gemstone is traditionally associated with each planet?

The classical associations are: Ruby for the Sun, Pearl for the Moon, Red Coral for Mars, Emerald for Mercury, Yellow Sapphire for Jupiter, Diamond (or White Sapphire) for Venus, Blue Sapphire for Saturn, Hessonite (Gomed) for Rahu, and Cat's Eye (Lehsunia) for Ketu. Each stone is chosen to match the qualities of its ruling planet — for example, Yellow Sapphire for Jupiter's wisdom and expansion, or Blue Sapphire for Saturn's discipline and restraint.