Why Are Gemstones Divided by Month? The Story Behind Birthstones

Why Are Gemstones Divided by Month? The Story Behind Birthstones

Every month of the year has its own gemstone. January has garnet, February has amethyst, and so on. But who decided this, and why? The answer mixes ancient religion, old beliefs about the stars, and a very modern business decision. This guide explains where birthstones came from, why the list has changed over time, and how to pick the right natural gemstone for any birth month.

Where the Idea of Birthstones Started

The Breastplate of Aaron

The earliest roots are in an ancient religious text. It describes a breastplate worn by the high priest Aaron, set with 12 gemstones. Each stone stood for one of the 12 tribes of Israel.

Linking Stones to Months and Zodiac Signs

Later writers connected those 12 stones to the 12 months of the year and the 12 signs of the zodiac. The idea was simple: each month has a stone, and that stone carries special meaning for people born then. Historians usually point to the writer Josephus in the 1st century and the scholar St. Jerome in the 5th century as early voices behind this link.

Wearing a Different Stone Each Month

Over time, the custom grew. By the 1700s, some people owned a full set of 12 stones and wore the stone for the current month. Later, the tradition shifted to wearing only the stone for your own birth month.

Why the Modern List Is the Way It Is

For a long time, different countries and traders used different lists. That caused confusion for buyers. In 1912, the main jewelry trade association in the United States published one standard list so that jewelers and customers would all use the same stones for each month.

The list has been updated since then:

• 1952: alexandrite, citrine, pink tourmaline, and zircon were added
• 2002: tanzanite was added for December
• 2016: spinel was added as a second stone for August

This is why many months now have two or three stones. Some stones were too rare or too expensive for most buyers. Adding more affordable choices gave everyone a way to wear their birthstone.

Birthstones by Month

Lists can differ slightly by country and by jewelry association.

Why Gemstones Are Still Divided by Month Today

People keep the tradition for three simple reasons.

It Makes a Gift Personal

A birthstone gift already has meaning built in. You do not have to guess someone’s taste, because the stone ties directly to who they are.

It Gives You Real Choice

With several stones for many months, buyers can pick a color, a budget, and a durability level that suits them.

It Connects Jewelry to a Story

Buyers today want jewelry that means something. A birthstone links a piece to a date, a person, and a tradition.

Pick Your Birthstone by Month

January: Garnet

Garnet comes in deep reds and rare pink-red shades. Browse our Garnet Gemstones collection.

February: Amethyst

Amethyst ranges from soft pink-purple to deep violet. See our Amethyst Gemstones collection.

March: Aquamarine

Aquamarine has a calm, sea-blue color. Explore our Aquamarine Gemstones collection.

August: Peridot and Spinel

August has two choices: bright green peridot and rare spinel. Browse our Spinel Gemstones collection or our Loose Gemstones collection for peridot.

October: Tourmaline

Tourmaline offers the widest color range of any birthstone, from pink to blue-green to bicolor. See our Tourmaline Gemstone Collection.

November: Citrine and Topaz

Citrine brings warm golden tones. Browse our Citrine Gemstone collection.

December: Blue Topaz

Blue topaz is a popular and strong choice for a December gift. Browse our Loose Gemstones collection.

How to Buy a Birthstone With Confidence

• Check the treatment. Some stones, like blue topaz, are commonly treated for color. Others, like tourmaline and amethyst, are often sold untreated. A good seller states this clearly on every listing.
• Check the hardness. For a ring worn daily, choose a stone with a Mohs hardness of 7 or higher.
• Think about the final piece. Not sure what to do with a loose stone? Our guide on how to design custom jewelry with a loose gemstone explains the whole process.
• Consider a matched pair for earrings. Browse our Gemstone Pairs collection.

Shop Birthstones at Onestep Gems

Every natural gemstone we sell lists its origin, size, clarity, and treatment, so you always know what you are buying. Orders over $120 ship free, and every purchase includes a 14-day exchange guarantee.

• All Loose Gemstones
• Tourmaline Gemstones
• Amethyst Gemstones
• Garnet Gemstones
• Gemstone Pairs

Frequently Asked Questions

Why are gemstones divided by month?
The idea began with 12 stones in an ancient religious breastplate. Later writers linked those stones to the 12 months and zodiac signs. In 1912, a standard modern list was published so buyers and jewelers used the same stones.

Who decided which gemstone belongs to which month?
There was no single ancient decision. Tradition shaped the lists over centuries, and the main U.S. jewelry trade association set the modern standard in 1912. It has been updated several times since.

Why do some months have more than one birthstone?
Some original stones were rare or costly. Adding extra options, such as tourmaline for October and spinel for August, gave buyers more colors and price points.

Is my birthstone different in other countries?
It can be. Some countries and associations keep slightly different lists, so you may see variations for certain months.

Do I have to wear only my own birthstone?
No. Many people wear their birthstone for its meaning, and many simply choose the color they love. Both are fine.

Is a birthstone a good gift?
Yes. It is personal and meaningful, and it works for birthdays, anniversaries, and milestones.