December Birthstones: Turquoise, Tanzanite, and Blue Zircon
December's stones are all blue, and all completely different: turquoise, worn for thousands of years from Egypt to the American Southwest; tanzanite, discovered in 1967 and found in only one place on earth; and zircon, a natural gem with fire approaching diamond's.
Choosing among them is mostly a matter of style and how the piece will be worn.
Turquoise, the ancient one
Turquoise is opaque sky blue to blue-green, often veined with its host rock in patterns called matrix. Clean robin's-egg blue, the Persian grade, has historically been most valued, though striking spiderweb matrix has its own following, especially in Southwestern work.
It is soft, 5 to 6 on the Mohs scale, and porous, so much commercial turquoise is stabilized with resin to protect the color and surface. Stabilized turquoise honestly labeled is standard; untreated natural gem-grade material costs several times more. Keep any turquoise away from perfume, lotion, and solvents, and it belongs in bezels rather than exposed settings.
Tanzanite, the newcomer
Tanzanite is a violet-blue found only in a few square miles near Mount Kilimanjaro. The finest stones show a deep blue with violet flashes that shifts with the light. Nearly all tanzanite is gently heated to bring out the blue; this is universal and accepted.
At 6 to 7 hardness with cleavage, tanzanite suits pendants and earrings perfectly and works in rings that are worn with some awareness. It offers a sapphire-adjacent look with more violet, usually at a lower price per carat.
Blue zircon, the sleeper
Zircon is a natural gemstone, no relation to cubic zirconia despite the unfortunate name. Blue zircon, produced by heating brown Cambodian material, shows brilliance and rainbow fire close to diamond's, in a vivid blue nothing else quite matches.
At 6.5 to 7.5 hardness but somewhat brittle on facet edges, it wears well in earrings and pendants and acceptably in protected ring settings.
Quick comparison
| Stone | Look | Hardness | Best homes |
|---|---|---|---|
| Turquoise | Opaque sky blue, matrix optional | 5 to 6 | Bezel rings, pendants, Southwestern styles |
| Tanzanite | Velvet violet-blue | 6 to 7 | Pendants, earrings, dress rings |
| Blue zircon | Vivid blue with fire | 6.5 to 7.5 | Earrings, pendants, protected rings |
Common questions
Zircon versus cubic zirconia?
Entirely different things. Zircon is a natural mineral mined from the earth; cubic zirconia is a manufactured diamond imitation. The name overlap is coincidence, and zircon deserves better than the confusion.
Will tanzanite run out?
The single known source is finite, and that scarcity story is real, though predictions of imminent exhaustion have come and gone. Buy it because the color moves you, not as an investment.
