December Birthstone
December's three blue stones
December has three birthstones: turquoise, zircon and tanzanite. All three are blue and all three sit on the modern US list, so any one is correct for a December birthday. They look very different: solid sky-blue turquoise, sparkling teal zircon, deep blue-violet tanzanite.
- Zircon — a real mineral, not the cubic zirconia sold as a stand-in for diamond. Blue zircon is often heat treated.
- Care — GIA warns off a daily tanzanite ring and says zircon abrades. Skin oils can discolor turquoise.
- Blue topaz — not one of December's three. GIA and the modern US list both put topaz in November.
- Have a blue stone you cannot name? Find out from a photo.
December is the only month with three official birthstones, and all three are blue: turquoise, the sky-blue stone worn for thousands of years; tanzanite, a violet-blue gem discovered only in 1967; and zircon, a brilliant natural gem whose blue form has fire to rival diamond. A December baby gets a choice — ancient and opaque, modern and velvety, or sparkling and vivid.
The three stones could hardly be more different in what they actually are: a copper mineral that never forms visible crystals, a rare variety of the mineral zoisite from a single hillside in Tanzania, and one of the oldest minerals ever dated on Earth. This page covers all three — what they are, why December's color is blue, how the list came to have three names on it, and how to tell the stones (and their imitations) apart.
The December birthstones
A copper phosphate mineral that forms opaque sky-blue to green-blue masses, often veined with the brown or black remnants of its host rock (the matrix). It is soft for a gem — about 5 to 6 on the Mohs scale — and has been mined and worn for over 5,000 years, from ancient Egypt to the American Southwest. Its color is so distinctive the stone named it: turquoise the color comes from turquoise the gem.
The blue-violet gem variety of the mineral zoisite, found commercially in exactly one place on Earth — the Merelani Hills at the foot of Mount Kilimanjaro in Tanzania, discovered in 1967. It is strongly pleochroic: tilt a cut stone and it shifts between blue and violet. Nearly all tanzanite is gently heated to bring out the blue, a standard and accepted treatment. At 6 to 7 on the Mohs scale it suits pendants and earrings better than daily rings.
A natural zirconium silicate — no relation to cubic zirconia, the lab-made diamond imitation, despite the confusingly similar name. Zircon is one of Earth's oldest dated minerals (Australian zircon grains have been dated to over 4 billion years) and one of its most brilliant natural gems: high refractive index and strong dispersion give blue zircon a fire few colored stones can match. Most blue zircon starts as brown material from Cambodia heated to a vivid teal-blue.
What color is the December birthstone?
The December birthstone color is blue — the one thing all three official stones share. But it is three different blues: turquoise is an opaque robin's-egg or sky blue, often leaning green; tanzanite is a transparent violet-blue with purple flashes; and blue zircon is a bright, sparkling teal-blue. Birthstone jewelry and charts usually represent December with a light-to-medium blue.
If you are matching a gift to "December blue," it helps to know the wearer: the earthy, bohemian look points to turquoise; a rich, formal violet-blue points to tanzanite; maximum sparkle on a budget points to blue zircon. Blue topaz — widely sold as a December stone and listed as an alternate on some charts — is a fourth, paler blue option, though it is not on the official modern list.
How December got its birthstones
Turquoise is the ancient root of December's claim to blue: it was set in Pharaoh Tutankhamun's burial mask, carved by Persian artisans, and holds a sacred place in Native American traditions of the Southwest. When the American National Association of Jewelers standardized the US birthstone list in 1912, December's stones were turquoise and lapis lazuli — two opaque blue stones of the ancient world.
The list has been revised twice since: zircon joined in the 1952 update, and in 2002 the American Gem Trade Association added the newly famous tanzanite — a stone that had not even been discovered when the original list was written. That is why December ended up with three stones where most months have one: each era added the blue gem of its time.
Choosing & caring for December birthstones
Practical notes for each: turquoise is porous and soft — keep it away from perfume, hot water and hard knocks, and be aware that much cheap "turquoise" is dyed howlite or reconstituted powder (our field guide shows the tells). Tanzanite's price rises steeply with color saturation; a deep violet-blue stone commands several times the price of a pale one. Blue zircon is the value pick — genuinely natural, brilliantly fiery, and far cheaper than tanzanite — but it is brittle at facet edges, so it prefers protective settings.
Frequently asked questions
What is the December birthstone?
December has three official birthstones, all blue: turquoise (the traditional stone, on the list since 1912), zircon (added 1952) and tanzanite (added 2002). Older charts also list lapis lazuli, and blue topaz appears on some charts as an alternate. Any of them is a "correct" December stone — the choice is aesthetic, not official.
What color is the December birthstone?
Blue. Turquoise is an opaque sky blue, tanzanite a transparent violet-blue, and zircon a brilliant teal-blue — so December charts and birthstone jewelry almost always use blue to represent the month.
Is zircon the same as cubic zirconia?
No — this is the most common December mix-up. Zircon is a natural mineral (zirconium silicate) mined from the earth and prized in its own right for centuries. Cubic zirconia is a laboratory-made diamond imitation (zirconium oxide) invented in the 1970s. They share nothing but a root word.
Which December birthstone is the most valuable?
Fine tanzanite is usually the most expensive per carat, driven by its single-source rarity — it is commercially mined only in one small area of Tanzania. Top natural-color blue zircon comes next, while turquoise varies enormously: most is affordable, but untreated, spiderweb-matrix material from famous mines (such as Lander Blue or Bisbee) can rival tanzanite prices.
How do I know if my blue stone is real turquoise?
The common fakes are dyed howlite or magnesite (look for dye concentrating in surface cracks) and reconstituted or stabilized powder. Real turquoise is cool and dense in the hand, takes no fingernail scratch, and its matrix veining runs through the stone rather than sitting printed on the surface. Photograph it with our identifier and read the turquoise field guide for the full set of checks.
See the full birthstones-by-month chart or jump to April, August, February, January, July, June, March, May, November, October, September.
Last updated 2026-07-18