Birthstone Calendar by Month

One Trade Group's Answer to a Marketing Problem

In 1912 the National Association of Jewelers sat down to solve a sales problem, not a mystery. Every store in America was naming a different stone for the same month, and a customer walking from one shop to the next got two different answers to the same question. The association picked one stone per month and asked the whole trade to use it. Alexandrite joined the list as a June option decades later, in 1952. Tanzanite followed for December in 2002, and spinel joined August in 2016, each addition arriving for the same reason as the first: a cheaper or easier-to-source stone for a month that had only one option before.

The Tide That Only Comes Once Every 21 Years

Pavitt's 1914 zodiac book puts a number on a phrase everyone already uses without knowing where it came from. Indian tradition, he records, held that the finest blue Moonstones only washed ashore when the sun and moon lined up in a rare alignment, once every three seven-year lunar cycles, 21 years apart. He states plainly that the phrase 'once in a blue moon' traces back to that tide, a wait measured in years, not a color at all. June's moonstone sits three cards over from Cancer's card on this calendar. The 21-year math behind the phrase does not show up on either card.

Four Places This Calendar Meets a Real Question

Real situations this calendar's month-and-zodiac split actually has to answer.

Two Signs Whose Zodiac Stone Belongs Elsewhere

Pavitt's 1914 zodiac chapters name specific gems for each sign. Two of this calendar's traditional-and modern-stone entries land on a different chapter once you check the page Pavitt actually wrote them on.

Three Records Behind the Calendar's Old-Tradition Notes

Citations for the moonstone, carbuncle, and Sepher de-Adam Kadmah material referenced above, each checked against page numbers already verified for this project.

1. Indian tradition held that the finest blue Moonstones surfaced only once every 21 years, at a rare lunar alignment, and Pavitt ties that belief directly to the English phrase 'once in a blue moon.'
   Pavitt 1914, p.182
   In his Cancer chapter, Pavitt writes that the sun and moon must reach a particularly harmonious alignment, recurring at three seven-year lunar intervals, before the tides wash up the finest stones, and states this is the belief he traces the common English idiom to.
2. Medieval legend, repeated by Chaucer and Mandeville among others, held that a large glowing carbuncle served Noah as a lamp inside the Ark.
   Pavitt 1914, p.232
   Pavitt's Scorpio chapter records this legend as part of the carbuncle's reputation for glowing in darkness, attaching a specific Biblical episode and two named medieval writers to the claim, not leaving it as unattributed ancient lore.
3. An 11th-13th century Hebrew text names twelve angels, one presiding over each month of the year, a month-by-month spiritual calendar distinct from both the 1912 U.S. month list and the zodiac-gem system.
   Kunz 1915, p.247
   Kunz dates the Sepher de-Adam Kadmah to no later than the 13th century and describes 'the twelve princes, set over the twelve months of the year,' starting with Nisan. He also records the legend that the angel Raziel engraved the book on a sapphire and gave it to Adam.

Sources & Editorial Basis

Month assignments follow the Jewelers of America birthstone list. Care guidance is checked against the Gemological Institute of America. Everything else here is folklore, astrology and crystal practice. We label each claim as tradition and name the text or the period we traced it to wherever one exists.

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Frequently Asked Questions

What are the 12 month birthstones?

January is garnet, February amethyst, March aquamarine, April diamond, May emerald, June pearl, July ruby, August peridot, September sapphire, October opal, November topaz, and December turquoise. These are the primary stones on the modern list used in the United States. Six of those months carry additional official stones, and several have an older traditional stone that differs from the modern one.

Which months have more than one birthstone?

Six do. March adds bloodstone, June adds alexandrite and moonstone, August adds spinel and sardonyx, October adds tourmaline, November adds citrine, and December adds tanzanite and zircon. June, August, and December each carry three. The extra stones were added over the last century, usually to give buyers an option at a lower price than the original stone.

What is the difference between modern and traditional birthstones?

The modern list is the one most American jewelers use today. It descends from a standardized list published in 1912 by the National Association of Jewelers, with additions in later decades. Traditional lists are older and vary by region and era, so March can be aquamarine or bloodstone and August can be peridot or sardonyx. Both are legitimate; they simply come from different eras.

Which birthstones are the rarest?

Alexandrite, by a wide margin. It changes color from green to red as the light changes, almost none of it turns up naturally, and most June alexandrite on sale was grown in a workshop. Tanzanite comes second and has only been on the chart since 2002. Among the primary twelve, fine emerald and deep red ruby are the two you will hunt longest for.

Is my birthstone based on my birth month or my zodiac sign?

Both systems exist and they answer different questions. The month system is the one behind almost all birthstone jewelry, and it changes on the first of each month. The zodiac system follows sun-sign date ranges, which begin between the 19th and the 23rd, so anyone born near the end of a month falls under the next sign. If you were born on August 30th your month stone is peridot and your zodiac sign is Virgo.

What is the difference between a birthstone calendar and a birthstone chart?

A birthstone calendar is built around the twelve months one at a time, so you open your own month and read it without scanning past the other eleven. A chart puts everything into a single table you compare side by side, including traditional alternatives and zodiac overlaps. Both hold the same data. Use the calendar when you want your month, and the chart when you want to compare months or check what an older list assigns.

Does the birthstone calendar change from year to year?

No. The month assignments do not reset with a new year, so the stone for your birth month does not depend on when you check. The modern list has only expanded, and rarely: tanzanite joined December in 2002 and spinel joined August in 2016. A calendar that disagrees with this one is almost always working from an older traditional list. This calendar follows the current modern one, tanzanite and spinel included.