December Birthstones

The current official modern list actually gives December three stones — turquoise, tanzanite, and zircon — after tanzanite was added in 2002 by the American Gem Trade Association, the first genuinely new stone added to any month in nearly a century at that point. This site keeps December to turquoise alone, since it's the pairing with by far the longest continuous history and the one most identified with the month in practice.

Turquoise is a copper-aluminum phosphate mineral, and its signature blue-green color comes from that copper content specifically — iron impurities can shift the color toward green, which is part of why turquoise from different mines has such visibly different character. It's one of the oldest gemstones used continuously by humans, with mining evidence in the Sinai Peninsula dating back roughly 6,000 years to ancient Egypt, and it holds deep, independent significance in Native American, particularly Navajo, Zuni, and Pueblo, traditions that long predate any European contact or birthstone list.

Persian turquoise, historically sourced from the Nishapur mines in what's now northeastern Iran, set the trade's quality benchmark for centuries — an intense, even, robin's-egg blue with minimal matrix veining. That standard still governs how turquoise is graded today, even though American Southwest mines (particularly in Arizona and Nevada) now supply much of the material actually sold, often with the darker matrix veining that's considered characteristic of Southwest turquoise rather than a defect.

Turquoise is genuinely porous, which makes it one of the more treatment-dependent gemstones on the market — most commercial turquoise is stabilized (impregnated with a clear polymer resin) to harden the surface and deepen the color, since untreated turquoise straight from most mines is often too soft and chalky to use in jewelry without this step. That's worth disclosing plainly: stabilized turquoise is standard trade practice, not a lesser or fake product, but it is a real, physical alteration to the stone worth knowing about before buying.

December spans the back half of Sagittarius and the first three weeks of Capricorn — genuinely the one month that touches three different signs across its full span if you count both edges, since Sagittarius itself begins in late November. Turquoise's protective, travel-related folklore (it was historically carried by travelers, particularly across desert routes, as a protective talisman) connects naturally to Sagittarius's own association with travel and exploration in astrological tradition.

Because of its porosity, turquoise needs distinctly different care from most other birthstones: avoid perfumes, lotions, and prolonged water exposure, all of which can be absorbed into the stone and dull or discolor it over time — a genuinely different maintenance profile from harder, non-porous December alternatives like zircon.

Turquoise's complete geology — including how to distinguish natural, stabilized, and reconstituted material — sits on its own dedicated crystal page, alongside tanzanite's separate and much more recently discovered mineralogy for anyone interested in December's newer modern-list addition.

Imitations are common at the low end of the turquoise market, and the most frequent by far is dyed howlite or dyed magnesite — both naturally white minerals with fine, dark veining that mimics turquoise's matrix convincingly once dyed blue. A hardness test isn't reliable for casual buyers, but a noticeably low price for a large, evenly saturated "turquoise" piece is usually the first honest warning sign.

"Reconstituted" turquoise — genuine turquoise fragments, powder, and dust bound together with resin and pressed into a solid, uniform block — is another common lower-cost product on the market; it's made from real turquoise material, but the process erases the natural matrix patterning entirely, producing an unnaturally even color and texture that experienced buyers learn to recognize.

Interestingly, matrix veining is judged in opposite directions by different markets: Persian-style buyers have traditionally preferred turquoise with little to no visible matrix, prizing pure, even color above all else, while American Southwest turquoise jewelry, particularly in Navajo silverwork, often celebrates a bold, visible matrix as part of the stone's individual character rather than treating it as a flaw to be minimized.