Birthstones by Month: A Complete Guide to All Twelve

By Lisa Chen, Founder · July 16, 2026

Short answer: the modern U.S. list runs garnet, amethyst, aquamarine, diamond, emerald, pearl, ruby, peridot, sapphire, opal, topaz, turquoise — but six of the twelve months carry more than one stone, and the list itself is a twentieth-century trade decision, not an ancient inheritance. Every birthstone chart online gives you the same twelve words. Almost none of them tell you where the list came from, why it has been revised three times since 1912, why the British list disagrees with the American one, or which of these stones is soft enough to be scratched by household dust. That is what this guide is for.

All twelve birthstones at a glance

Here is the whole list in one place, with the modern U.S. stones, the 1912 originals where they differ, and the hardness of each. I have kept the hardness figures to what the USGS mineral gemstone tables and GIA actually publish, rather than the rounded numbers that circulate on chart pages.

Month	Modern U.S. stone(s)	1912 U.S. list	Mohs hardness
January	Garnet	Garnet	6.5–7.5 (USGS)
February	Amethyst	Amethyst	7 (USGS, quartz)
March	Aquamarine, bloodstone	Bloodstone, aquamarine	7.5–8 (USGS, beryl)
April	Diamond	Diamond	10 (USGS)
May	Emerald	Emerald	7.5–8 (USGS, beryl)
June	Pearl, moonstone, alexandrite	Pearl, moonstone	2.5 pearl (GIA); 6–6.5 moonstone; 8.5 alexandrite (USGS)
July	Ruby	Ruby	9 (USGS, corundum)
August	Peridot, spinel, sardonyx	Sardonyx, peridot	7 peridot; 8 spinel (USGS)
September	Sapphire	Sapphire	9 (USGS, corundum)
October	Opal, tourmaline	Opal, tourmaline	5–6.5 opal (GIA); 7–7.5 tourmaline (USGS)
November	Topaz, citrine	Topaz	8 topaz; 7 citrine (USGS)
December	Turquoise, zircon, tanzanite	Turquoise, lapis lazuli	5–6 turquoise; 7.5 zircon (USGS); 6–7 tanzanite (GIA)

Read the second and third columns against each other and the shape of the last century falls out: seven months — January, February, April, May, July, September and October — carry exactly the stones they were handed in 1912. Everything that changed, changed for a reason someone recorded.

Where this list actually came from

The honest version is less romantic than the marketing version. Birthstone lists are old — the historical tables compiled from the gemologist George Frederick Kunz show wildly different stones circulating from the fifteenth to the twentieth centuries. June was cat's eye, turquoise and agate. July was turquoise and onyx. December was bloodstone and ruby. Not one of those matches what a jeweler would sell you today.

The list you actually see in stores dates to August 1912, when the national jewelers' trade association — the body that became today's Jewelers of America, which still describes itself as the originator of the official list and dates it to 1912 — met in Kansas City and adopted a standard. Sources differ on the association's exact name at the time; what they agree on is that it is JA's predecessor.

Then it moved three more times:

• 1952. The list was revised: alexandrite joined June, citrine joined November, zircon replaced lapis lazuli in December, and March's two stones swapped order so aquamarine led and bloodstone followed. Sources disagree about which industry body enacted this revision, so I am not going to attribute it to one; what is not in dispute is that it happened in 1952 and what it changed.
• 2002. Tanzanite was added to December — the first genuinely new addition in fifty years, and a stone that had not been discovered when the 1912 list was written.
• 2016. Spinel was added to August, announced jointly by the American Gem Trade Association and Jewelers of America.

None of this is a scandal. It is just worth knowing that the "ancient" birthstone tradition your chart is selling is, in its current form, a trade standard that was last edited in 2016. These lists are assembled by the trade, and the trade decides when they change.

The clearest proof that these lists are conventions rather than facts is that they disagree across borders. The British list published in 2013 gives April as diamond and rock crystal, May as emerald and chrysoprase, July as ruby and carnelian, September as sapphire and lapis lazuli, and October as opal alone — no tourmaline. Same months, same planet, different stones. If a birthstone were a property of the month, this could not happen.

Why six months have more than one stone

This is the question the chart pages never answer, and the answer is history stacked on history. A month ends up with two or three stones through one of three routes.

The first is addition without subtraction. When alexandrite was added to June in 1952, pearl and moonstone were not removed. When spinel was added to August in 2016, peridot and sardonyx stayed. The list grows because taking a stone away from people who already own it is bad business.

The second is supply. A birthstone has to be something a jeweler can reliably sell twelve months a year. Alexandrite is instructive: GIA describes it as a rare variety of chrysoberyl and notes that because of its scarcity, especially in larger sizes, it is relatively expensive. A month whose only stone is rare is a month a jeweler cannot serve, so an affordable companion earns its place.

The third is inheritance. Sardonyx sits in August because it was August's stone long before peridot was. March is the same story: bloodstone held the month first, aquamarine joined it by 1912, and the 1952 revision simply promoted the newcomer to the front without evicting the original. December kept turquoise from the old lists while gaining zircon and then tanzanite on top. So when a retailer tells you your month has two or three stones, that is true, and it is not a trick to sell you more — it is a hundred years of committee decisions nobody ever cleaned up.

Month by month

Each month below gets the stone, the one durability or treatment fact I would want a friend to know, and a link to the full guide.

January — garnet

Garnet is not one mineral. The USGS lists it as a group of silicate minerals spanning a hardness of 6.5 to 7.5, covering almandine, pyrope, spessartine, grossular, tsavorite, demantoid and more — which is why "garnet" covers everything from deep red to vivid green. That range matters: two stones both honestly sold as garnet can sit a full point apart on the hardness scale. Full January guide.

February — amethyst

Amethyst is the purple variety of quartz, Mohs 7, and GIA rates its toughness good and calls it suitable for all jewelry types. The one caveat worth carrying: GIA notes that some amethyst color can fade with prolonged exposure to intense light. A ring worn daily in strong sun is a different proposition from one kept in a drawer. Full February guide.

March — aquamarine and bloodstone

Aquamarine is the blue variety of beryl at 7.5–8 Mohs, the same mineral species as emerald with none of emerald's fracture problem. GIA's treatment guide is candid that much aquamarine is blue-green as it comes out of the ground and is heated to remove the greenish component. Bloodstone, a dark green chalcedony, is the month's older stone and led the 1912 list. Full March guide.

April — diamond

Diamond is the hardest natural material at Mohs 10, and April is where the three-category confusion does the most damage. Cubic zirconia and moissanite are simulants — look-alikes with, in GIA's words, very different chemical composition and crystal structure. A laboratory-grown diamond is not a simulant; it is diamond. The FTC requires each to be described for what it is. Full April guide.

May — emerald

Emerald is beryl again, 7.5–8 Mohs, and it is the clearest case on the list of hardness lying to you. GIA rates emerald's toughness only fair to good and states plainly that some estimates state that 90 percent or more of emeralds are fracture-filled. That is GIA's own hedge, and I am repeating it as an estimate rather than a measurement. The practical consequence is firm: no ultrasonic cleaner, no steam. Full May guide.

June — pearl, moonstone and alexandrite

June is the widest spread on the entire list. GIA puts pearl at 2.5 on the Mohs scale — the softest birthstone by a distance — and notes it can be damaged by many chemicals and all acids, a list that includes hair spray, perfume, cosmetics and perspiration. Moonstone is a feldspar at 6–6.5 per the USGS. Alexandrite is chrysoberyl at 8.5, the third-hardest stone on the whole list, and the rarest. One month, three stones, and a six-point hardness gap between them. Full June guide.

July — ruby

Ruby is red corundum, Mohs 9, second only to diamond among these stones and genuinely built for daily wear. The disclosure to ask about is filling: GIA's treatment guide describes rubies whose numerous surface-reaching fractures are filled with glass, and notes that in some cases the amount of filler glass can be significant. Heating, by contrast, is routine and GIA calls it durable and permanent. Full July guide.

August — peridot, spinel and sardonyx

Peridot is the gem form of olivine at Mohs 7 per the USGS. Spinel, the 2016 addition, is Mohs 8 and has a genuinely good story: the USGS still lists its red variety under the old trade name "Balas ruby," and on announcing the addition, the American Gem Trade Association's chief executive said spinel was revered by ancient merchants under that name and that it was not until the late eighteenth century that spinel could be distinguished as a separate mineral from ruby. Sardonyx, the oldest of the three, is a banded chalcedony from the quartz family, which the USGS places at 7. Full August guide.

September — sapphire

Sapphire is corundum too — the same mineral as ruby, Mohs 9. GIA's rule is simple: red corundum is ruby, and every other color, including colorless, is sapphire. Expect heat: GIA's treatment guide says heating can intensify, or even induce, a blue coloration in sapphires, and that pale sapphires once discarded during mining are treated to a desirable blue. Full September guide.

October — opal and tourmaline

Opal is the fragile one: GIA gives it 5 to 6.5 Mohs, rates its toughness very poor to fair, and warns that heat from intense light can cause fracture lines called crazing. Opal is also commonly assembled — GIA describes doublets, a thin layer of opal cemented to a backing, and triplets, opal cemented between a clear top and a backing. Those are legitimate products that sell for a fraction of solid opal, but you should know which one you are buying. Tourmaline, at 7–7.5, is the sturdier October option. Full October guide.

November — topaz and citrine

November is the treatment month. On blue topaz, GIA is unambiguous: because strong blue colors do not occur naturally in topaz, such stones are considered to have undergone irradiation treatment, and GIA describes irradiation as extremely frequent for topaz. On citrine, GIA's own FAQ says that because yellow quartz colors are rare in nature, most citrine is the result of heating, which converts less valuable shades of purple amethyst to the golden shades of citrine. Topaz is also the best example of the hardness trap: Mohs 8, and GIA still rates its toughness poor because of its cleavage. Full November guide.

December — turquoise, zircon and tanzanite

December carries three stones and the most recent history. Turquoise is 5–6 Mohs; GIA notes some turquoise is treated to improve its surface appearance, and that it can be discolored by cosmetics and even skin oils. Zircon is 7.5, and GIA notes some reddish brown zircons are heated to produce more commercially viable colors, including an intense blue. Tanzanite is 6–7 with fair to poor toughness and cleavage, and GIA states it is routinely heat-treated from brownish to blue-violet — a treatment GIA calls stable with no additional durability concerns. Full December guide.

The two things worth knowing before you buy any of them

Everything above collapses into two ideas that no birthstone chart teaches, and both are the difference between a piece you still wear in five years and one you do not.

First: hardness is not toughness. Hardness is resistance to scratching, and that is all it is. Toughness is resistance to chipping and breaking, and it is a separate property. Topaz sits at Mohs 8, harder than quartz, harder than tourmaline — and GIA rates its toughness poor, because topaz has basal cleavage and a hard knock can split it along that plane. Tanzanite has the same problem; emerald has a version of it where the fractures are already inside the stone. A high Mohs number tells you the stone will not scuff in your jewelry box. It does not tell you it will survive a door frame.

There is a second, more useful way to read the Mohs number, and GIA hands it to you almost in passing on its amethyst page: common substances like sand and dust are composed mostly of quartz. Quartz is 7. That single fact turns the scale into a practical threshold — anything below about 7 can, in principle, be abraded by ordinary household dust over years of wear. Look back at the table with that in mind and the twelve months sort themselves. Diamond, ruby, sapphire, alexandrite, spinel, topaz, aquamarine, emerald and zircon sit at or above the dust line. Garnet and tourmaline straddle it. Moonstone, opal, turquoise, tanzanite and above all pearl sit below it — which does not make them bad stones. It makes them stones that want a pendant or an occasional-wear ring rather than a band you never take off.

Second: treated does not mean fake. This is the one I most want to land, because the internet has convinced people that a heated stone is a scam. It is not. Heat treatment of the gems GIA lists is, in GIA's words, considered durable and permanent under normal handling conditions. Most citrine is heated amethyst. Strong blue topaz is irradiated. Much aquamarine is heated to drop its green tone. These are ordinary, long-standing trade practices producing genuine stones.

What actually matters is the disclosure, and the U.S. rule here is more specific than most people assume. The FTC's guidance on the Jewelry Guides says sellers should tell consumers about gemstone treatments in certain circumstances: if the treatment is not permanent, the seller should say so; if it requires special care, the seller should say so; and even where a treatment is permanent and creates no special care requirement, the seller should disclose it if it significantly affects the stone's value. So a shop that does not label its citrine "heated" is not automatically breaking a rule — but a shop that cannot tell you when you ask is telling you something anyway.

Which brings me to the three words people mash together, and the one distinction I would fix in the whole category if I could fix only one:

• Treated — a real, natural stone whose colour or clarity was altered. Heated sapphire is sapphire.
• Lab-grown (synthetic) — made in a laboratory, but per GIA it shares virtually all chemical, optical and physical characteristics of its natural counterpart. Lab-grown ruby is ruby. It must be disclosed, and the FTC bars the unqualified word "ruby" for it — but it is the real material, and calling it a fake is simply wrong.
• Simulant (imitation) — a look-alike. GIA defines a simulant as a material such as CZ that looks like another gem and substitutes for it but has very different chemical composition, crystal structure and optical and physical properties. GIA notes CZ can be produced in almost any colour and that coloured CZ makes good imitations of red, purple, blue, green or black gemstones, and gives its prevalence as common. A CZ "emerald" is not an emerald at any price.

Those three are not a spectrum. They are three different answers to "what is this?", and a seller who blurs them is doing it on purpose. If you take one habit from this guide, take this one: ask which of the three you are holding, and ask before you pay.

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A note on birthstone meanings

I am going to be straight with you, because this is where most birthstone content quietly stops being honest. Birthstones carry a large body of traditional lore — stones have been associated for centuries with protection, health, prosperity, love and particular temperaments, and that lore is a real and genuinely interesting part of cultural history. It is also, as far as anyone can demonstrate, exactly that: cultural history. There is no evidence that a stone influences your luck, health, wealth, relationships or personality, and I am not going to imply otherwise to sell you one.

That is not a reason to skip birthstone jewelry. A stone tied to the month someone was born is a lovely reason to choose one piece over another, and meaning that comes from the person who gave it to you is the durable kind. It just is not a property of the mineral. When you read that a stone is "traditionally believed to bring courage," read the whole phrase — the belief is the fact being reported, not the courage.

The same applies to star-sign stones, an older and separate tradition that does not line up with the month list at all — see our guides to the Capricorn, Cancer and Scorpio stones.

Frequently asked questions

What are the birthstones for each month?

The modern U.S. list is: January garnet, February amethyst, March aquamarine and bloodstone, April diamond, May emerald, June pearl and moonstone and alexandrite, July ruby, August peridot and spinel and sardonyx, September sapphire, October opal and tourmaline, November topaz and citrine, and December turquoise and zircon and tanzanite. Six months carry more than one official stone. Other countries publish different lists; the British list, for example, gives October opal alone and adds carnelian to July.

Why do some months have three birthstones?

Because the list was revised three times and stones were added without old ones being removed. June gained alexandrite in the 1952 revision on top of pearl and moonstone; December gained zircon in 1952 and tanzanite in 2002 on top of turquoise; August gained spinel in 2016 on top of peridot and sardonyx. Supply is the other reason: alexandrite is rare and, per GIA, relatively expensive, so a month cannot practically rely on it alone.

Are birthstone meanings real?

The traditions are real and old; the effects are not demonstrated. Stones have been associated for centuries with qualities like protection, prosperity or courage, and that lore is a genuine part of cultural history worth knowing. But there is no evidence that wearing a particular stone changes your luck, health, wealth, relationships or personality. Treat "traditionally believed to" as a report about what people have believed, not a claim about what the stone does.

Which birthstones are the most durable for everyday wear?

By hardness, diamond leads at Mohs 10, followed by ruby and sapphire at 9, alexandrite at 8.5, then topaz and spinel at 8. But hardness is only half the answer: GIA rates topaz's toughness poor because of its cleavage, so it chips despite its high number. The most genuinely everyday-proof stones on the list are diamond, ruby, sapphire and spinel. Pearl at 2.5, opal at 5 to 6.5, and turquoise at 5 to 6 are the ones that need the most protection.

Is my citrine or blue topaz fake if it was treated?

No. Per GIA, most citrine is the result of heating amethyst, and strong blue colours do not occur naturally in topaz, so blue topaz is considered irradiated — GIA calls irradiation extremely frequent for topaz and notes blue topaz colour tends to be very stable. Both are genuine stones. A treated stone is not the same thing as a simulant such as CZ, which is not the stone at all. What you are entitled to is disclosure: the FTC says sellers should tell you about a treatment when it is not permanent, when it requires special care, or when it significantly affects the stone's value.

If there is one rule that survives this entire list, it is that the number on the chart is never the whole stone: ask what it is, ask what was done to it, and ask whether it is hard enough and tough enough for the way you actually live. From here, the deepest months are worth reading in full — start with November, where nearly every stone is treated, and June, which spans six points of hardness in one month.

If you want to wear a birthstone rather than read about one, our Personalized Cross & Birthstone Necklace is made in all twelve months — 18k gold plating over a 316L stainless steel base, built for daily wear. The stones are cubic zirconia, not mined gems, and the product page says so.