LunaDecember's main stone — the turquoise
Ask whether a turquoise has been stabilised and watch what happens next. Most of what sells has been: the raw stone is chalky and porous enough to soak up hand cream, so it is pressure-impregnated with clear resin to harden it and hold the colour. That is normal practice rather than a fake, and it costs a fraction of untreated material — but it should be said out loud, and a seller who cannot answer has told you something anyway. The same test works on the other thing a counter will offer, which is that turquoise guards travellers or draws off illness: an honest answer calls that an old story and points anybody with a real health worry at a doctor. Two questions, and you know most of what you need about the shop.
Then there is the counterfeit proper, and it is everywhere: howlite, a cheap white mineral with grey veining that takes blue dye beautifully. Dyed howlite makes convincing beads, and the giveaway is usually price and perfection — a heavy strand of flawless, evenly coloured “turquoise” for pocket money is not turquoise. “Reconstituted” or block turquoise is a third category, real powder glued back together: honest enough when it is labelled, and worthless when it is not.
The black or brown webbing running through many stones is matrix — the host rock the turquoise grew inside. Taste splits along old lines here: the Persian ideal was an even sky blue with none of it showing, while American collectors pay a premium for a dense “spiderweb”. Neither is a quality grade, so choose by eye, and read “Persian” on a modern tag as a description of colour rather than a claim about a country.
The other stones listed for December
Zircon is the December stone people misread most often, because the name sounds like cubic zirconia and the two have nothing in common. Cubic zirconia is a laboratory diamond substitute, worked out at the Lebedev Physical Institute in Moscow in the seventies and mass-produced ever since — worth almost nothing. Zircon is a natural mineral, dense and full of fire; it bends light so strongly that you can see doubled facet edges looking down through the top, and the blue in shop windows is brown Cambodian material that has been heated. Grains of the same mineral, as it happens, are the oldest solid things ever dated on this planet, at roughly 4.4 billion years.
Tanzanite came out of a few hills near Merelani in Tanzania in 1967 and has never turned up in commercial quantity anywhere else: one deposit, one country, the entire world supply. It reached the December list in 2002, thirty-five years after it was found, which makes it comfortably the newest entry on a chart otherwise built from stones people have worn for millennia. Nearly all of it is heated from brown to that violet-blue, and it is strongly pleochroic — turn a cut stone and it moves from blue to violet to a reddish tone, which is why cutters orient it so carefully. Turquoise, meanwhile, also leads the Sagittarius stones for birthdays through 21 December; from the 22nd the sign is Capricorn, while tanzanite — younger than the chart it joined — belongs to no zodiac tradition at all.
What the turquoise actually is
Turquoise is a copper aluminium phosphate that forms only where copper-bearing water seeps through aluminium-rich rock in a desert, which is why the map of it reads like a list of dry places: Sinai, where Egyptian expeditions cut it four thousand years ago; Nishapur in Iran, source of the even sky blue that set the standard for everyone else; and the American Southwest, where Nevada and Arizona mines fed the silverwork trade.
The most famous of those, Sleeping Beauty in Arizona, stopped producing gem turquoise in 2012, and prices for its clean matrix-free blue have climbed every year since — a reminder that these are finite holes in the ground rather than products with a production line. At Mohs 5 to 6 turquoise is among the softest things on the chart, about the hardness of a steel blade, which is the real reason it is set into bezels and cuffs instead of raised solitaires.
The December stone as a gift
December birthdays lose out to the holidays, and a three-stone month is genuinely useful there: turquoise for something with silver and character, zircon for real sparkle at a low price, tanzanite when both the budget and the occasion are serious. If the present has to double as a Christmas gift, split it — one stone in December, the other in the birthday card, and neither one gets swallowed by the tree.
Hardness decides the format here, and it decides fast. Turquoise sits at Mohs 5 to 6 and tanzanite cleaves, so both want a bezel, a cuff or a chain rather than a raised ring on a working hand; zircon is harder but brittle at the edges and chips if it is set proud. Keep all three away from perfume, hot water and ultrasonic cleaners. The quickest way to spoil a good December present is to hand it over with no instructions at all and let somebody wear it to wash up.
Where the month chart came from
Nothing in geology or astronomy ties a mineral to a page of the calendar. The chart everyone quotes was agreed by American jewellers in 1912, in Kansas City, so that shops across the country would sell one list rather than twelve. It has been edited since: alexandrite, citrine, tourmaline and zircon were added in 1952, and tanzanite joined December as late as 2002 — thirty-five years after the stone was first dug up in Tanzania.
So when two shops give you two different stones, neither of them is lying. British lists keep bloodstone for March where American ones print aquamarine. June carries pearl from the old custom and moonstone plus alexandrite from the newer one. Read any of these charts as a custom with a paper trail — a dated commercial agreement — and not as a fact about the person born that month.
Month or star sign: two different lists
The month stone and the zodiac stone belong to different traditions: one is a jewellers' chart, the other is astrology, where the stone is derived from the ruling planet and the element. Two signs fall inside December: Sagittarius stones (through December 21) and Capricorn stones (from December 22). We do not repeat the astrology here — that reading lives on the sign pages.
At a glance
| Attribute | Value |
|---|---|
| Month | December |
| Main stone | Turquoise |
| Alternates | Zircon, Tanzanite |
| Star signs | ♐ Sagittarius (through December 21), ♑ Capricorn (from December 22) |
| Source of the list | Jewellers’ chart, USA, 1912 (revised 1952 and 2002) |
Frequently asked questions
What is the December birthstone?
In the jewellers' chart the December birthstone is the turquoise, with zircon and tanzanite listed as alternates. There is no single canon — traditional and modern charts differ — so no choice from that set is wrong.
Is zircon the same thing as cubic zirconia?
No — the similar names are all they share. Zircon is a natural mineral, mined for centuries, heavy for its size and unusually fiery. Cubic zirconia is a synthetic developed in the seventies to imitate diamond and costs almost nothing. A blue zircon has been heated from naturally brown material, which is standard, permanent and nothing to worry about.
How do I tell real turquoise from dyed howlite?
Start with price and perfection: an even, flawless blue strand sold for next to nothing is dyed howlite or reconstituted powder, because real turquoise varies stone to stone and costs money. Dye also pools darker in the veins, the reverse of the natural pattern, where the veining is the host rock. Beyond that, ask outright whether a piece is natural, stabilised or reconstituted, and buy where the answer comes in writing.
The month-by-month chart is a 20th-century jewellery custom, not science: no link between a mineral and a birth date has ever been demonstrated. Stones do not heal and do not steer events — health questions belong with a doctor, not with a pendant. The stone images on this page are generated illustrations, not photographs of particular specimens.
A reading from your date, not your month
Everyone born in the same thirty days shares this stone. In the app, Luna builds a reading from your full birth date instead: strengths, talents, a forecast for the day — and tells it by voice.
Open Luna