Zodiac Stones: The Gemstone of Each Sign and Why Lists Differ

The story starts in Exodus 28, with the breastplate of the high priest Aaron. It was a square of woven cloth set with twelve stones in four rows of three, each engraved with the name of one of the twelve tribes of Israel. The biblical text says nothing about the stars. The link to the sky came later.

In the first century, two Jewish writers working in Greek made the connection. Philo of Alexandria read the twelve stones as an image of the zodiac, with the four rows as the four seasons. The historian Josephus wrote that the stones could stand for the months of the year or for the twelve signs. The number fit, and the idea stuck. The Book of Revelation adds twelve precious stones in the foundations of the New Jerusalem, and medieval Christian writers commented on each one at length.

One problem runs through the whole history: nobody knows for certain which stones sat on the breastplate. The Hebrew names were translated differently into Greek, Latin and modern languages, and Josephus himself gave two different lists. Ancient stone names also pointed to different minerals than they do today. Most scholars think the stone the ancients called sapphire was lapis lazuli, the blue stone with golden flecks that Pliny the Elder described. No modern list can claim to reproduce the breastplate exactly.

Wearing one stone for your birth month is much younger than the breastplate. The American gemologist George F. Kunz traced it to 18th-century Poland, while the Gemological Institute of America points to Germany in the 16th century. Either way, the custom is only a few centuries old.

The list most people know today was fixed in August 1912, when the National Association of Jewelers, now Jewelers of America, met in Kansas City and adopted one stone or two for each month. It has changed several times since:

• In 1952 the Jewelry Industry Council of America added alexandrite to June, citrine to November and pink tourmaline to October, and replaced lapis lazuli with zircon in December.
• In 2002 the American Gem Trade Association added tanzanite to December.
• In 2016 that association and Jewelers of America added spinel to August.

Most modern zodiac lists borrow from these month stones with one simple rule: each sign takes the birthstone of the month that holds most of its days. Aries runs from March 21 to April 19, so it has 19 days in April and 11 in March, and it takes April's diamond. Capricorn runs from December 22 to January 19 and takes January's garnet. Applied to all twelve signs, the rule gives the first column of the table below. If you only know a birth month, the post on the April zodiac sign shows how a single month splits between two signs.

Kunz is also the source of a second, separate zodiac list. In his 1913 book The Curious Lore of Precious Stones, he printed one stone per sign: bloodstone for Aries, sapphire for Taurus, agate for Gemini, emerald for Cancer, onyx for Leo, carnelian for Virgo, chrysolite for Libra, beryl for Scorpio, topaz for Sagittarius, ruby for Capricorn, garnet for Aquarius and amethyst for Pisces. Set it beside the older month lists and a pattern shows: almost every one of these stones was a traditional birthstone of the month in which the sign begins. Bloodstone was a March stone, sapphire an April one, garnet a January one. The modern rule looks at the month that holds most of the sign's days instead, so the two lists often name the same gem one sign apart. When one website gives Taurus sapphire and another gives Taurus emerald, this is usually the reason.

A third layer comes from the ruling planets. Old astrology gave each planet a color and a metal: gold and yellow to the Sun, silver and white to the Moon, iron and red to Mars, copper and green to Venus, lead and black to Saturn. From there come moonstone for Cancer, the Moon's sign, citrine and tiger's eye for Leo, the Sun's sign, red jasper for Aries under Mars and black onyx for Capricorn under Saturn.

The loosest layer is the element. Many recent lists give blue and green stones to the water signs, warm reddish stones to the fire signs, opaque earthy stones to the earth signs and pale, clear stones to the air signs. This pairing changes from writer to writer more than any other.

The result is that two careful lists can name different stones for the same sign, and none of them has the authority to overrule the rest. The easiest way to read them is as layers: the month stone, the 1913 stone and the planet stone.

The table gives each sign's usual dates and element, the modern month stone, the stone from Kunz's 1913 list and other stones that often appear. Sign boundaries can move by a day from year to year, so if your birthday sits near one, check your exact sign for your year.

The table uses your Sun sign, the sign the Sun stood in when you were born. Chrysolite is an old name that most often meant what we now call peridot, and beryl is the mineral family that includes emerald and aquamarine.

Each sign below gets its stones and the logic the tradition gives for them. The sign profiles cover the temperament in full.

Aries. For Aries, the first fire sign, modern lists give diamond, April's stone. Its hardness is often matched with the sign's directness. Kunz chose bloodstone, a dark green chalcedony with red spots, which has been a March birthstone for centuries and is still on the March list today. Red jasper comes from Mars, the ruler, and its color.

Taurus. Taurus takes May's emerald. Venus rules Taurus, and green was Venus's color in old astrology, like copper, her metal, which turns green with age. Rose quartz appears for the same planet in a softer tone. Kunz gave the sign sapphire instead, an old April stone.

Gemini. Gemini gets pearl from June. Pearl grows inside a mollusk and is organic, so it is not a mineral, yet it has been on the birthstone list since 1912. Kunz's agate, an old May stone with its side-by-side bands of color, is often read as the twins and the changeable mind of Mercury, the ruler. Alexandrite, added to June in 1952, changes color under different light and is picked for the same reason.

Cancer. Cancer has ruby from July on the modern list and emerald on Kunz's, the one row where his choice matches no older stone of June. Moonstone, with its bluish sheen, comes from the Moon, Cancer's ruler. Pearl often joins it: white like the Moon and born in water, the element of the sign.

Leo. Leo takes August's peridot, a yellowish green stone. Because the Sun rules Leo, many lists add yellow and golden stones, citrine and tiger's eye with its silky bands. Kunz gave Leo onyx, which older lists placed in July.

Virgo. For Virgo, September's sapphire is a hard blue stone that lists match with a patient earth sign. Kunz chose carnelian, an orange to reddish brown chalcedony from the older August lists. Mercury also rules Virgo, so some lists borrow Gemini's agate.

Libra. Libra gets opal and pink tourmaline, both October stones. Opal flashes many colors in one stone, which modern lists tie to Libra's love of balance and harmony. Pink tourmaline belongs to Venus, Libra's ruler as well as Taurus's. Kunz gave chrysolite, the old stone of September.

Scorpio. Scorpio takes November's topaz, usually golden yellow, and citrine, the month's second stone. For its intense, private side, newer lists choose obsidian, a black volcanic glass, the most recent pairing and the least consistent from source to source. Kunz gave beryl, the mineral family of aquamarine, which older lists placed in October.

Sagittarius. Sagittarius takes turquoise from December, one of the oldest stones worn as jewelry. Blue and violet belong to Jupiter, the ruler, which is why tanzanite, added in 2002, fits here too. Kunz chose topaz, the stone the month rule gives to Scorpio.

Capricorn. For Capricorn, January's stone is garnet, usually deep red. Saturn, the ruler, had black and lead in old astrology, so black onyx comes second and smoky quartz sometimes third. Kunz gave Capricorn ruby, a December stone on the older lists.

Aquarius. Aquarius has amethyst, February's violet stone. Its Greek name means "not drunk," after an old belief about wine. Kunz chose garnet, which the month rule gives to Capricorn. Aquamarine appears for the water bearer in the sign's image, even though Aquarius is an air sign.

Pisces. Pisces takes March's aquamarine, whose Latin name means "seawater," a natural fit for the last water sign. Kunz chose amethyst, also a violet stone of Jupiter, the traditional ruler of Pisces. Bloodstone, March's second stone, completes the list.

In the trade, diamond, ruby, sapphire and emerald are usually called precious, and the rest, from amethyst to turquoise, semi-precious. The split is old and reflects how rare stones were centuries ago. Gemologists use it less and less, since some so-called semi-precious stones are rarer than many sapphires. For zodiac stones the label hardly matters: every list mixes both groups, and every sign in the table has at least one semi-precious stone.

A zodiac stone makes a good symbolic gift, because it shows you paid attention to the day someone was born. A few practical points help.

1. Check the sign first. Someone born on April 19 or December 21 can fall on either side of the line depending on the year and the hour. The post on the zodiac cusp explains why.
2. Choose by color. If a sign has two or three stones, each is equally valid in the tradition, so pick the shade the person likes.
3. Think about wear. On the Mohs hardness scale, diamond is 10, ruby and sapphire 9, topaz 8, amethyst 7, opal and turquoise between about 5 and 6.5 and pearl between 2.5 and 4.5. Harder stones hold up in a ring worn every day, and softer ones are safer in earrings or a pendant.
4. Tell the story. A short note on why the stone belongs to the sign, through the month, the 1913 list or the planet, makes the gift personal.

Many sellers attach claims about health, luck or money to stones. No study has confirmed any of them, and the custom itself began as a symbol, a name carved into a stone and a color matched to a planet. That is still the best way to wear one.

A zodiac stone follows a single point in your chart, the Sun. Astrology also reads the Moon, the rising sign and every planet, and the same Sun sign looks different from one person to the next. The birth chart calculator works out all of those positions from your date, time and place of birth, and the zodiac fundamentals guide explains how signs, elements and planets fit together. Read it all as a tradition of interpretation that describes tendencies and leaves the choices to you.