Ask an astrologer why Aries is impatient and the answer is one word: Mars. Ask why Taurus loves comfort and the answer is Venus. Every sign is ruled by a planet, and the planet's nature is the sign's nature. Once you know your ruler you know your sign more deeply than any list of traits can tell you, and you also know, because the same planet governs stones, fingers and days, exactly how to choose a gem.
The traditional rulers
Classical astrology used seven planets and gave each of them one or two signs. The Sun rules Leo and the Moon rules Cancer, the two signs of high summer. The other five planets each rule a pair of signs on either side: Mercury rules Gemini and Virgo, Venus rules Taurus and Libra, Mars rules Aries and Scorpio, Jupiter rules Sagittarius and Pisces, and Saturn rules Capricorn and Aquarius. The pattern is symmetrical, and it is the one Vedic astrology still uses without change.
The modern rulers
When Uranus, Neptune and Pluto were discovered, Western astrologers assigned them to signs: Uranus to Aquarius, Neptune to Pisces and Pluto to Scorpio. Most now treat these as co-rulers alongside the traditional planets, so Scorpio is "ruled by Mars and Pluto". The traditional rulers remain the ones used for practical matters, gemstones included, because the outer planets have no stones, days or fingers in the old system.
What each ruler brings
- Mars gives Aries and Scorpio their drive, courage and temper. Its day is Tuesday, its metal copper, its stones red coral and bloodstone.
- Venus gives Taurus and Libra their love of beauty, comfort and harmony. Friday, silver, diamond and opal.
- Mercury gives Gemini and Virgo their quick minds and quick tongues. Wednesday, silver or gold, emerald and aqeeq.
- The Moon gives Cancer its moods, memory and devotion to home. Monday, silver, pearl and moonstone.
- The Sun gives Leo its warmth, pride and presence. Sunday, gold, ruby.
- Jupiter gives Sagittarius and Pisces their faith, generosity and appetite for the larger world. Thursday, gold, yellow sapphire and feroza.
- Saturn gives Capricorn and Aquarius their discipline, patience and detachment. Saturday, silver or iron, blue sapphire and amethyst.
The ruler and the finger
Each planet also has a finger, and this is where astrology meets palmistry. Jupiter's finger is the index, Saturn's the middle, the Sun's the ring finger, Mercury's the little finger, and Venus and Mars share the thumb and its base. A stone is worn on its planet's finger so that it sits over the mount of that planet in the palm. A Sagittarius wearing yellow sapphire on the index finger is placing Jupiter's stone on Jupiter's mount, which is why the tradition is so specific about fingers.
Two signs, one planet
Where a planet rules two signs, it shows a different face in each. Mars in Aries is open and direct; Mars in Scorpio is hidden and patient. Venus in Taurus is sensual and possessive; Venus in Libra is refined and social. Mercury in Gemini talks; Mercury in Virgo analyses. Jupiter in Sagittarius explores; Jupiter in Pisces believes. Saturn in Capricorn builds; Saturn in Aquarius reforms. The element of the sign, fire, earth, air or water, is what changes the planet's expression.
Using your ruler
If you know nothing else about your chart, your ruling planet is enough to start with. Its day is the day to begin new things and to first wear a stone. Its stone is the safe first gem to try. Its mount in your palm is the one to look at first, because a strong mount means the ruler is working well for you, and a flat one means it needs support. Everything more detailed, the Moon sign, the ascendant, the transits, refines this; none of it replaces it.