April Birthstone: Diamond, and the Honest Alternatives

By Lisa Chen, Founder · July 16, 2026

Short answer: April’s birthstone is diamond — and that single word covers three different things once you start shopping. Mined and lab-grown diamonds are both genuinely diamond. Cubic zirconia and moissanite are not diamond at all; they are simulants, different materials that happen to look the part. Every April shopper is really asking one thing underneath: what am I actually getting for my money? This guide draws the three lines using the definitions the industry and the law run on.

Diamond is April’s stone, and the list is younger than the lore

The birthstone list Americans use is trade history, not ancient law. It was standardized in 1912 by the national jewelers’ trade association known today as Jewelers of America, which still publishes it. Some months picked up extra stones later — June and December carry three apiece — but April has stayed one word long: diamond.

The lore runs much older. According to GIA, the fascination started in India, where diamonds were traded as early as the fourth century BCE, and the name comes from the Greek adamas, meaning “invincible.” A second-century poet claimed the stone warded off the evil eye; later centuries believed it an antidote to poison. I offer that as history — things people have believed, part of why the stone matters. It is not a claim that a diamond will do anything for your health, luck, or love life.

What actually counts as a diamond

“Diamond” has a real definition rather than a marketing one. The FTC’s Jewelry Guides, at 16 CFR Part 23, put it in a sentence: a diamond is a mineral consisting essentially of pure carbon crystallized in the isometric system, with a hardness of 10, a specific gravity of approximately 3.52, and a refractive index of 2.42.

Notice what is missing: the word natural. That is not an oversight — the definition describes what the material is, not where it came from. GIA puts the same stone from the science side: diamond is the only gem made of a single element, typically about 99.95 percent carbon, in an isometric crystal structure. Meet that description and you are a diamond. Miss it, and no amount of sparkle gets you in.

The three things the word can mean on a price tag

Here is the whole map. Two are diamond, two are not, and the gap is not quality — it is substance.

What it is	Material	Mohs hardness	Is it a diamond?
Mined diamond	Carbon, isometric crystal	10	Yes
Lab-grown diamond	Carbon, isometric crystal (grown by HPHT or CVD)	10	Yes — must be labeled “laboratory-grown”
Moissanite	Silicon carbide	9.25	No — a simulant
Cubic zirconia	Zirconium oxide	8.5	No — a simulant

• Lab-grown diamond is diamond. GIA puts it directly: like their natural counterparts, laboratory-grown diamonds have the same crystal structure, consisting of tightly bonded carbon atoms, which results in nearly the same chemical, optical and physical properties as natural diamonds. Telling them apart takes laboratory instruments reading the growth history, not a jeweler’s loupe. GIA grades them and laser-inscribes the girdle as laboratory-grown. It is younger and it costs less. It is not a fake, and I will not call it one.
• Simulants are a different kingdom. GIA defines a simulant as a material that looks like another gem and substitutes for it, but has very different chemical composition, crystal structure, and optical and physical properties — the diamond simulants, in GIA’s words, are completely unrelated to diamonds at the atomic level. Cubic zirconia is grown from powdered zirconium oxide melted in a metal chamber; moissanite is silicon carbide. Neither is carbon; neither is diamond.

So the honest word for a stone is one of four: mined, lab-grown, moissanite, or cubic zirconia. Anything vaguer is doing work for the seller, not for you.

Why 8.5 and 10 are further apart than they look

The USGS puts diamond at 10 on the Mohs scale, the top of a ten-mineral reference scale. The crucial word in the USGS description is relative: hardness is described relative to those ten minerals. It is a ranking, not a ruler — each step says which mineral scratches which, not by how much.

That matters at the top, where the steps stop being even. Cubic zirconia at 8.5 and diamond at 10 look like neighbors on paper; in absolute terms the jump into diamond is the largest on the scale by a wide margin. So when a listing says “8.5, nearly as hard as diamond,” the arithmetic is doing something the mineralogy does not support.

The honest limits of cubic zirconia, including ours

Let me name its weaknesses.

• It yellows. GIA states it plainly in its guide to simulants: CZ will yellow in color over time. Not might. That is the best reason to treat CZ as a piece you will eventually replace rather than an heirloom.
• It is softer than diamond, and hands take a beating. At 8.5, CZ is genuinely hard and durable — GIA says so — but everyday knocks dull its facets on a timeline a diamond never runs.
• It sparkles differently. GIA notes CZ has slightly more fire but less brilliance than diamond — it sparkles unlike what it imitates.

None of that makes CZ a bad buy. GIA’s own line is the one I would put on our packaging: purchasing a simulant can be a great option as long as it is an informed decision.

The same honesty applies to what the stones sit in. Our pieces are 18k gold-plated over 316L stainless steel — plated, not solid gold, and low-nickel rather than nickel-free, since the steel holds its small nickel content in the alloy and releases very little. If you want something to wear through showers and sweat without fussing, our rings are built for that. If you want a diamond, buy a diamond, from a jeweler who hands you a grading report.

Treated diamonds, and why the paperwork matters

Even inside real diamond there is a second disclosure question, because color and clarity can be altered. GIA sorts treatments by whether they last. Irradiation, annealing, HPHT, and laser drilling are stable, and GIA reports them — annealing is so routine that most black diamonds are treated. Coating and fracture filling are not stable, and GIA grades neither: coatings scratch and wear off, and fracture filling can be damaged by ordinary steam, acid, or ultrasonic cleaning. Retailers must disclose treatments, so a seller who cannot tell you is a seller to walk away from.

How to read an April birthstone label

• An unqualified “diamond” means diamond. Using the word for anything that misses the definition is deceptive — a $30 “diamond” ring tells on itself.
• Lab-grown must say so — “laboratory-grown,” “laboratory-created,” or a maker’s-name equivalent, immediately before the word diamond and equally conspicuous.
• Simulants must say “imitation” or “simulated” — and the Guides note that “faux” is not an adequate disclosure.
• “Birthstone” is a regulated word too. The Guides name “birthstone” alongside “gem” and “gemstone”: you may not call a lab-grown or simulated stone a “birthstone” unless the disclosure sits immediately beside it. “April birthstone ring” on a CZ piece, with no other wording, is exactly the gap that rule was written for.
• “Real,” “genuine,” and “natural” are off-limits for anything produced artificially — which is why a lab-grown diamond, though truly diamond, is not a “natural” one.

Caring for whichever stone you chose

GIA says a diamond is usually durable enough for an ultrasonic cleaner, but an inclusion-heavy or treated stone wants a lint-free cloth, or warm water with mild soap and a soft brush. That gentler routine suits CZ and moissanite too: much of what dulls a CZ is lotion film rather than damage, so cleaning buys the sparkle back until the yellowing catches up.

Frequently asked questions

What is the April birthstone?

Diamond, and only diamond. It is the sole stone on the April line of the official U.S. birthstone list published by Jewelers of America, standardized in 1912. Unlike June or December, April has never picked up a second official stone.

Is a lab-grown diamond a real diamond?

Yes. A lab-grown diamond has the same crystal structure of tightly bonded carbon atoms as a mined diamond, and GIA reports nearly the same chemical, optical and physical properties. GIA grades it and laser-inscribes it as laboratory-grown. It is a real diamond with a different origin and a lower price, and it must be labeled as lab-grown.

Is cubic zirconia a diamond?

No. Cubic zirconia is zirconium oxide, a lab-made simulant; GIA describes diamond simulants as completely unrelated to diamonds at the atomic level. It is legitimate to buy and wear when labeled honestly, but it is not a diamond and should never be sold as one.

Is moissanite a diamond?

No. Moissanite is silicon carbide, a different material. It is the hardest common diamond simulant at 9.25 on the Mohs scale, but it is doubly refractive and throws more than twice the fire of diamond, so it does not read as diamond to a trained eye.

Will a cubic zirconia April birthstone ring last forever?

No, and no honest seller should imply it will. GIA states that CZ yellows over time, and at 8.5 on the Mohs scale it takes surface wear a diamond would not. Treat it as something you enjoy now and replace later, and it is a good buy.

April got the stone with the strictest definition, which is either a burden or a gift depending on who writes the label. The rule I would hand a friend: make the seller pick one of four words — mined, lab-grown, moissanite, or cubic zirconia. A seller who will say which one is a seller you can trust on everything else. For the same naming trap in reverse, see our December birthstones guide, where natural zircon gets confused with cubic zirconia, and our October birthstone guide, where softness is the whole story. If you would rather just leave a piece on, our waterproof jewelry is built to stay on.

If you want to wear April’s stone rather than read about it, our Personalized Cross & Birthstone Necklace is made in a April version — 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.