To identify your birthstone, look up the calendar month of your birth on two separate lists side by side: the current modern list maintained by the Gemological Institute of America and the American Gem Society, and a separate traditional list compiled from older references that frequently disagree with each other. The answer is rarely a single gem. Six months — March, June, August, October, November, and December — carry more than one stone on the modern list, so anyone born in those months has a genuine choice rather than a single assigned gem. Birthstones are assigned by month, which means the exact day of your birth never changes the result; a date field is only a convenience for filling in the month you were born in. The modern list has been revised in documented steps since 1912, and the year each modern stone was officially added is part of the answer, not extra noise. Getting all of that right on a single page is the job of a dedicated lookup rather than a guess from memory.
Why identifying a birthstone is harder than it looks
Most birthstone charts online show one neat gem per month. That tidiness is misleading and is the single most common error people run into when they try to identify which birthstone belongs to them or someone they are buying for. The current list published by both the Gemological Institute of America and the American Gem Society contains more than one stone for six months out of twelve. June is the most cited example, with three modern stones — pearl, alexandrite, and moonstone — rather than the single pearl that simplified charts usually print. The same multi-stone pattern holds for August (peridot, spinel, sardonyx), December (turquoise, tanzanite, zircon), October (opal and tourmaline), November (topaz and citrine), and March (aquamarine alongside bloodstone).
If you were born in any of those six months, identifying your birthstone is not a matter of remembering a single name. It is a matter of knowing which list you are looking at and what that list actually says. A second source of confusion is the word "traditional." Traditional charts genuinely disagree from source to source, and some circulating versions are internally inconsistent, listing stones that could not have been traditional at all. Anyone identifying a birthstone from memory, or from a chart that does not state its sources, is guessing.
The two lists you need to compare
The current modern list descends from a list adopted by the American National Association of Jewelers in 1912 and has been revised in documented steps since. It favours transparent faceted gemstones. The version used in a sound lookup follows the current Gemological Institute of America chart and the American Gem Society chart, which were compared month by month and agree completely, including on all six multi-stone months. That agreement is what allows the modern column to be stated plainly without hedging.
Traditional charts reflect older custom and are not standardised. Rather than picking one house version and presenting it as settled, a careful lookup shows only the stones that two independent references both list — the International Gem Society chart and the Brilliant Earth birthstone guide. Where those two references differ, that difference is shown rather than hidden. This matters for identification because the two lists disagree on specific months in specific ways. March on the traditional side is bloodstone rather than the aquamarine most modern charts lead with. August on the traditional side is sardonyx rather than peridot. December on the traditional side is turquoise and lapis lazuli rather than turquoise, tanzanite, and zircon.
| Birth month | Modern birthstones | Traditional birthstone(s) |
|---|---|---|
| March | Aquamarine, bloodstone | Bloodstone |
| June | Pearl, alexandrite, moonstone | Alexandrite, pearl, moonstone |
| August | Peridot, spinel, sardonyx | Sardonyx |
| October | Opal, tourmaline | Opal, tourmaline |
| November | Topaz, citrine | Topaz, citrine |
| December | Turquoise, tanzanite, zircon | Turquoise, lapis lazuli |
In most of those cases the traditional stone is also present on the modern list, which is why the modern list often gets quoted as if it were the only one. December is the partial exception: turquoise is shared, but lapis lazuli was the December stone on the modern list until 1952, when zircon displaced it. If you are identifying a birthstone you were given as a gift and it does not match the modern chart, the traditional chart is the next place to check, not a sign that the stone is wrong.
How to identify a birthstone by month
The fastest reliable method is to use a lookup that shows both lists at once rather than a chart that collapses everything to one stone. A practical tool for that is the Birthstone Finder, which lets you choose a month or paste a full date and returns the modern and traditional rows side by side, plus the documented addition year for each modern stone. The steps are:
- Select a birth month from the list, or use the optional date field and the month will be filled in for you.
- Read the modern birthstones first, remembering that six months legitimately carry more than one stone.
- Compare against the traditional row, and check the addition note to see which modern stones arrived in 1952, 2002 or 2016.
The optional date field does not change the result. Birthstones are assigned by calendar month, so a birthday on 1 March and a birthday on 31 March both return the same stones; the date field is only there so you can type a birthday you already know instead of working out which month to select. If the page reports a single stone for your month, that is the answer; if it reports two or three, those are your real options under the current modern list.
What the addition dates tell you
The modern list is younger than people assume. It was adopted in 1912 and has been revised in documented steps since. The addition years for the modern stones that arrived after 1912 are part of the identification story, because they explain why stones that sound "ancient" are in fact twentieth- or twenty-first-century additions. Alexandrite was added to June, tourmaline to October, citrine to November, and zircon to December in 1952, with zircon displacing lapis lazuli for December at the same time. Tanzanite joined December in 2002. Spinel joined peridot for August in 2016.
| Year of official addition | Stone added | Month affected |
|---|---|---|
| 1952 | Alexandrite | June |
| 1952 | Tourmaline | October |
| 1952 | Citrine | November |
| 1952 | Zircon (displacing lapis lazuli) | December |
| 2002 | Tanzanite | December |
| 2016 | Spinel | August |
The documented addition years of 1952, 2002 and 2016 are recorded in trade histories such as National Jeweler's evolution of the birthstone list. Where a stone has a sourced addition year, a sound lookup shows it; where no addition year could be sourced, no year is shown, because inventing a plausible date would be worse than leaving the field blank. That matters if you are told your "traditional" December birthstone is lapis lazuli. You are not being lied to — lapis lazuli was the December stone on the modern list until 1952, when zircon replaced it. Tanzanite, added in 2002, is younger still, and spinel for August is the most recent addition, in 2016.
Limits the lookup will not resolve
Three things are deliberately out of scope, and knowing them keeps you from misusing the tool. There is no day-level answer: birthstones are assigned by calendar month, and no widely accepted birthstone standard varies by day within a month, so the tool does not pretend otherwise. There is no zodiac-sign list: birthstones assigned by Western zodiac sign rather than by calendar month are a separate, less settled tradition and are not mixed in here. There is no authenticity grading: birthstones are a cultural and commercial convention rather than a natural fact, so for a real purchase the stone and its treatment should be confirmed with a qualified jeweller or a gemological laboratory report rather than taken on the strength of a chart lookup alone.
How the tables are kept honest
Behind the lookup, two twelve-row tables do the actual work. The modern table was built by comparing the current Gemological Institute of America and American Gem Society charts month by month and accepting only entries where both agree. The traditional table is the intersection of two independent references — the International Gem Society chart and the Brilliant Earth guide — so that stones listed by only one source are not shown as if they were settled. Month selection is validated to one through twelve, and the optional date entry parses an ISO date, rejects impossible days including 29 February outside a leap year, and then uses only its month, since birthstones carry no day-level precision. Seventeen golden cases across both tables, plus length, uniqueness and non-empty invariants, guard against a reordered or truncated table. The lookup runs entirely in the browser; nothing you enter is uploaded, stored or logged.
Reading the result for a multi-stone month
If you were born in March, June, August, October, November or December, the page will return more than one modern stone for your month. That is not an error. It means the modern list genuinely offers more than one choice for that month, and the traditional row offers at least one more. A simple rule of thumb: if you are buying for someone, ask whether they prefer the traditional stone (often a deeper-coloured, opaque or banded gem) or the more recent modern addition (often a brighter or more transparent gem). If you are identifying a stone you already own, the traditional row is the place to start when the modern row does not match, because some older pieces predate the 1952, 2002 and 2016 additions and were set with what was then the assigned stone. Where the two rows agree, the identification is consistent with both reference sets the tool was built on, and you can treat the answer as settled for cultural purposes.
For a deeper look, see Does Exact Birth Date Change Your Birthstone by Month?.