Birthstone for December: Turquoise.

Blue-Green · Healing, protection, wisdom

Overview & Meaning

December closes the year with a trio of breathtaking blue gemstones: turquoise, tanzanite, and zircon. Turquoise, the oldest recorded birthstone of the trio, has been prized for more than 5,000 years across ancient Egyptian, Persian, and Native American civilizations as a sacred talisman of healing, heavenly protection, and enduring wisdom. Its distinctive sky-blue to robin's-egg green hue has defined jewelry design from Pharaohs’ burial masks to southwestern silver squash blossom necklaces.

Joining turquoise is tanzanite—a modern gemological sensation discovered in 1967 in the foothills of Mount Kilimanjaro and added to the official birthstone list in October 2002 by the American Gem Trade Association. Tanzanite dazzles with hypnotic trichroism, shifting from deep royal blue to shimmering purple and burgundy. Completing the trio is zircon, one of the oldest minerals on planet Earth, delivering diamond-like brilliance and dispersion. Together, December’s stones represent deep contemplation, transformative discovery, and spiritual elevation.

Mineralogical & Geological Profile

Turquoise

Chemical Formula

CuAl6(PO4)4(OH)8 · 4H2O (Turquoise) / Ca2Al3(SiO4)3(OH) (Tanzanite) / ZrSiO4 (Zircon)

Mineral Species / Class

Phosphate (Turquoise) / Zoisite (Tanzanite) / Silicate (Zircon)

Mohs Hardness

5.0 – 6.0 (Turquoise) / 6.0 – 7.0 (Tanzanite) / 6.0 – 7.5 (Zircon)

Crystal System

Triclinic (Turquoise) / Orthorhombic (Tanzanite) / Tetragonal (Zircon)

Geological Formation & Origin

Turquoise is a secondary mineral that forms when acidic copper-rich groundwater percolates downward through aluminum- and phosphorus-bearing sedimentary or volcanic rocks in arid climates. Tanzanite is geologically unique to a tiny 4-kilometer strip of land in the Merelani Hills of northern Tanzania, formed by metamorphic folding and hydrothermal fluids rich in vanadium. Zircon is an extraordinary geochronometer: microscopic zircon crystals discovered in the Jack Hills of Western Australia have been dated via uranium-lead isotopic dating to 4.404 billion years old—the oldest solid fragments of Earth’s crust ever discovered.

History, Lore & Symbolism

King Tutankhamun’s famous gold burial mask was elaborately inlaid with vivid Persian turquoise, and Persian rulers believed turquoise rings prevented accidental injury. Tanzanite entered the world stage after its 1967 discovery by prospector Manuel d'Souza; Tiffany & Co. recognized its magnificence and named it in 1968 after its country of origin. In October 2002, AGTA added tanzanite to December—the first update to the official birthstone list since 1952. Zircon, long misidentified as cheap cubic zirconia in popular perception, possesses intense optical dispersion (0.039) and double refraction that made it a revered ancient gem for bringing honor, wisdom, and safe harbor.

Durability, Care & Cleaning

Turquoise is relatively soft (5.0–6.0 Mohs) and porous; keep it away from perfumes, cosmetics, oils, and household detergents, which can alter its blue color. Tanzanite (6.0–7.0 Mohs) has a directional cleavage that requires gentle setting and protection from sharp blows; never clean tanzanite in ultrasonic or steam cleaners. Zircon (6.0–7.5 Mohs) can be brittle along facet edges. Clean all three stones with mild soap, lukewarm water, and a soft microfiber cloth.

Frequently Asked Questions

Q1 When was tanzanite added to the December birthstone list?

In October 2002, the American Gem Trade Association (AGTA) officially added tanzanite to the December birthstone roster, making it the first new gemstone added to the official industry list since 1952.

Q2 Is natural zircon related to cubic zirconia?

No. Zircon is a completely natural, ancient zirconium silicate mineral (ZrSiO4) found in the Earth's crust, while cubic zirconia (ZrO2) is a synthetic, laboratory-created diamond simulant invented in the 1970s.