The December birthstones are tanzanite, zircon and turquoise. Each is a different mineral, and they differ in color, hardness, rarity and price. All three are on the modern birthstone list recognized by the GIA.
This guide covers what each one is, how to tell them apart, and which suits what you want to do with it.
The three December birthstones at a glance
| Tanzanite | Zircon | Turquoise | |
|---|---|---|---|
| Color | Blue to violet | Blue, colorless, red, orange, yellow, brown, green | Blue to green, usually with matrix veining |
| Hardness (Mohs) | 6–7 | 6–7.5 | 5–6 |
| Where it comes from | Merelani Hills, Tanzania — nowhere else on earth | Sri Lanka, Australia, Myanmar, Vietnam, Cambodia | Iran, Arizona, Nevada, China |
| Usual treatment | Heat, to bring out blue and violet — permanent | Heat, for blue and colorless | Dye, resin stabilization, cavity filling |
| Best worn as | Earrings and pendants | Pendants and occasional-wear rings | Pendants, earrings, protected settings |
The practical takeaway: none of the three is a hard stone. All three should be kept out of ultrasonic and steam cleaners. Warm soapy water and a soft brush is the correct method for every one of them.
Tanzanite
Tanzanite is the youngest gemstone on any birthstone list — it was only discovered in 1967. It comes from a single place: the Merelani Hills in northern Tanzania, an area of a few square kilometers. There is no second deposit anywhere in the world.
Color. Pure, rich blue is the most valuable. Most tanzanite leans violet, and the stone is strongly pleochroic — it shows different colors depending on the angle you look through it, which is why cutting orientation matters so much to the final appearance.
Treatment. Nearly all tanzanite on the market is heated. In the ground the material is usually a brownish zoisite; heat converts it to blue and violet, and the change is permanent and stable. Heated tanzanite is the normal, accepted product, not a defect.
Hardness and wear. 6–7 on the Mohs scale, with a cleavage direction that makes it vulnerable to a sharp knock. Tanzanite is a fine choice for earrings, pendants and occasional-wear rings, and a poor choice for a ring worn every day without a protective setting.
View our tanzanite — loose stones, each filmed in 4K macro.
Zircon
Zircon has a reputation problem caused entirely by a name. Zircon is a natural mineral. Cubic zirconia is a man-made diamond simulant. They are unrelated, and the confusion costs natural zircon a lot of the respect it deserves.
Natural zircon is one of the oldest minerals on earth. Some crystals from Western Australia date to over four billion years, older than any other terrestrial material found.
Color. Zircon occurs in red, orange, yellow, brown, green, blue and colorless. Blue is the variety most associated with December, and it is produced by heating brown material from Cambodia and Vietnam.
Why it looks the way it does. Zircon has a high refractive index and strong dispersion, the property that splits white light into spectral colors. In a well-cut stone this produces a fire few other gems match. Colorless zircon was used as a diamond substitute long before synthetic materials existed, and the reason was optical, not economic.
Hardness and wear. 6–7.5, but with a tendency to abrade at facet edges. It holds up better than tanzanite but still belongs in settings that protect the girdle.
View our zircon — natural blue and neon zircon, each stone filmed in 4K macro.
Turquoise
Turquoise is the oldest of the three by thousands of years. It has been mined and worn since at least 3000 BC, and it carries more cultural weight than almost any other gemstone, in Persian, Egyptian, Tibetan and Native American traditions alike.
Color. Blue through green, usually crossed by the dark veining of the host rock, called matrix. The most prized material is an even, unveined robin’s egg blue historically associated with the Nishapur district of Iran. Matrix is not a flaw; for many buyers it is the point.
Treatment. Turquoise is porous and relatively soft, so most commercial material is treated. Stabilization with epoxy or acrylic resin hardens the stone and fixes the color. Dyeing and cavity filling with metal-loaded epoxy are also common. Untreated, natural-color turquoise of good quality is genuinely scarce and priced accordingly.
Hardness and wear. 5–6, the softest of the three, and porous on top of that. It absorbs oils, cosmetics and perspiration, which change its color over time.
Which December birthstone should you choose?
If you want the strongest color: tanzanite. Nothing else on this list produces that blue-violet, and the single-source rarity is real rather than marketing.
If you want brilliance and fire: zircon. A well-cut blue or colorless zircon out-sparkles both of the others by a wide margin.
If you want history and character: turquoise. It is the least durable of the three, but it is the only one your great-grandmother might have recognized.
If it is going into a ring worn every day: none of them, honestly, without a protective setting. All three are softer than sapphire or ruby. A bezel or halo setting solves it; a raised solitaire does not.
Frequently asked questions
Why does December have three birthstones?
Birthstone lists were standardized commercially rather than scientifically, and they have been revised several times. Tanzanite was only added in 2002, thirty-five years after the stone was discovered. Turquoise and zircon are the older entries.
Is zircon the same as cubic zirconia?
No. Zircon is a natural mineral, zirconium silicate, formed in the earth. Cubic zirconia is a synthetic material made in a laboratory as a diamond simulant. They share part of a name and nothing else.
Is heated tanzanite still real tanzanite?
Yes. Almost all tanzanite is heated, the treatment is permanent and stable, and it is disclosed as standard trade practice. A reputable seller will state it on the certificate.
Which December birthstone is the most valuable?
Fine tanzanite in a strong, pure blue generally commands the highest prices per carat, particularly in larger sizes. Exceptional untreated turquoise can also reach high prices, but the market is far narrower.
Can I wear a December birthstone every day?
In earrings or a pendant, yes, all three. In a ring worn daily, only with a setting that protects the stone. All three are below the hardness where a gem shrugs off knocks and grit.
What is the birthstone for December 12, December 29 or any other date in December?
Birthstones are assigned by month, not by day. Anyone born on any date in December shares the same three birthstones: tanzanite, zircon and turquoise.
What color is the December birthstone?
Blue. Tanzanite is violet-blue, the zircon most associated with December is blue, and turquoise ranges from sky blue to greenish blue.
December Birthstones at MYGEMSET
Every loose stone we sell is filmed in 4K macro so you can see exactly what you are buying, and lab certificates are shown on the stone’s page where available.
Not sure how to read a lab report? See our gemstone certification guide.