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Something blue.

December Birthstone, Turquoise, Tanzanite, and Zircon

Four blue stonesMohs 5 to 8Read the label

The December birthstone is turquoise, tanzanite or zircon, with blue topaz on many modern charts, so December gets four shades of blue to choose from. Each one is a different mineral, and most are treated in some way, so read the label before you buy a raw crystal as a gift.

What is the December birthstone

The December birthstone list grew over the last century: turquoise came first, zircon joined it, tanzanite was added in 2002, and blue topaz appears on many modern charts. GIA's December birthstone page covers turquoise, tanzanite and zircon as gems. For the rest of the year, see the birthstone chart.

December birthstone color

The December birthstone color is blue, from the sky blue of turquoise to the violet blue of tanzanite. Zircon for December means bright blue zircon, and blue topaz runs from icy pale to deep inky blue. Off the jewelry counter the colors widen: turquoise also comes in greener shades colored by iron, and natural zircon grows brown, red, yellow and green.

Turquoise, the original December birthstone

Turquoise is the original December birthstone, a hydrous copper aluminum phosphate that forms where water seeps through copper-bearing rock in dry country. It is soft (Mohs 5 to 6) and porous, which is why so much of it is stabilized with resin, dyed, or replaced outright by dyed howlite or magnesite. Iran, the Sinai and the American Southwest have produced it for centuries, and the name comes from the French for Turkish stone, after the trade route that carried it to Europe.

Tanzanite, from one place on Earth

Tanzanite comes from one place on Earth, the Merelani Hills near Mount Kilimanjaro in Tanzania, where it was found in 1967. It is the blue to violet variety of the mineral zoisite, about 6.5 on the Mohs scale, and it shows different colors from different directions: blue, violet and a reddish brown. Most tanzanite is heated to clear out brownish tones and leave the blue and violet. Tiffany & Co. named it and launched it in 1968.

Zircon, not cubic zirconia

Zircon is not cubic zirconia: zircon is a natural zirconium silicate, while cubic zirconia is a lab-made zirconium oxide used as a cheap diamond stand-in. Zircon rates about 7.5 on the Mohs scale and has fire close to a diamond's. Most blue zircon is brownish zircon heated to blue. Zircon is also the oldest mineral known from Earth: crystals from the Jack Hills of Western Australia are about 4.4 billion years old, and geologists date rocks by the uranium zircon traps as it grows. Wikipedia's zircon article has the science.

Blue topaz for December

Blue topaz for December is the hardest of the four at Mohs 8, and one of the least expensive. Nearly all of it starts as colorless topaz that is irradiated and heated into the shades sold as sky, Swiss and London blue. Natural blue topaz exists, but it is usually pale.

Raw December birthstone gifts

Raw December birthstone gifts take some label reading, because all four stones are often treated:

  • Turquoise: a natural, unstabilized nugget is the prize. Ask whether a piece is stabilized, dyed or reconstituted, and pass on bright, perfectly even blue that turns out to be dyed howlite.
  • Tanzanite: rough tanzanite is often brownish or grayish blue before heating, and an honest label says whether it was heated.
  • Zircon: small natural crystals with pyramid ends, usually brown to red, are affordable, while blue ones have been heated.
  • Blue topaz: bright blue raw crystals are treated; natural raw topaz is usually colorless, pale blue or sherry.

December birthstone meaning

The December birthstone meaning in lore is protection and good fortune, carried mostly by turquoise. Turquoise has been worn as an amulet from ancient Egypt and Persia to the Native peoples of the American Southwest, and medieval Europeans said zircon brought sound sleep, wealth and wisdom. Tanzanite is too new for old legends. That is belief and history, not chemistry.

December Birthstone: Turquoise, Tanzanite and Zircon FAQ

Why does December have four birthstones?

December birthstones have grown to four because the US list was updated over time, adding zircon and then tanzanite to turquoise, while blue topaz became a popular extra.

Is zircon the same as cubic zirconia?

Zircon is not the same as cubic zirconia: zircon is a natural mineral, and cubic zirconia is a synthetic made in a lab.

Can turquoise get wet?

Turquoise can get wet briefly, but it is porous, so do not soak it, and keep it away from oils, lotions and long hot sun.

Which December birthstone is the hardest?

The hardest December birthstone is blue topaz at Mohs 8, followed by zircon, tanzanite and finally turquoise, the softest at 5 to 6.

Sources