Zodiac.
The twelve-sign celestial wheel used in Western astrology to map the sun's apparent path through the year.
The zodiac is the band of sky that follows the sun's apparent path through the year, divided into twelve signs of thirty degrees each. The word comes from the Greek zodiakos kyklos, "circle of little animals," and most of the signs do indeed take their names from creatures: ram, bull, crab, lion, scorpion, fish, and so on. Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces complete the wheel.
The system as used in modern Western astrology is tropical: the signs are anchored to the seasons, starting at the spring equinox in the northern hemisphere, rather than to the actual constellations behind them. Sidereal astrology, used in Vedic tradition, anchors to the constellations themselves and so produces slightly different sign dates.
In crystal work the zodiac shows up as a long-standing system of correspondences. Each sign has traditional stones (sometimes several), drawn from a mix of medieval lapidary lore, planetary rulerships, and modern association. The pairings are best treated as starting points for reflection rather than fixed prescriptions.