December has three birthstones: turquoise, tanzanite, and zircon. Turquoise is an opaque blue-to-green stone, tanzanite a blue-violet zoisite found only in Tanzania, and zircon a brilliant natural gem, not cubic zirconia.
Tanzanite has only one commercial source in the world: the Merelani Hills of northern Tanzania, where mines reach “over 300 feet deep into the earth,” according to the Gemological Institute of America (GIA).
Zircon is a natural mineral and a different material from cubic zirconia, the synthetic diamond simulant with a similar name. Zircon was used in jewelry centuries before cubic zirconia existed. All three December birthstones are commonly blue, which makes blue the classic December birthstone color. The UK list gives turquoise and tanzanite but not zircon.
What are the December birthstones?
Turquoise, tanzanite, and zircon are all official December birthstones on the GIA list; the British list gives turquoise and tanzanite. The table compares the three.
| Property | Turquoise | Tanzanite | Zircon |
|---|---|---|---|
| Material | Turquoise (opaque mineral aggregate) | Zoisite (blue-violet variety) | Zircon (zirconium silicate) |
| Mohs hardness | 5–6 | 6–7 | 6–7.5 |
| Toughness | Fair to good | Fair to poor; has cleavage | Fair to good; brittle facet edges |
| Colors | Blue to green, often with matrix veins | Pure rich blue to violet | Blue, colorless, red, orange, yellow, brown, green |
| Main sources | China (Hubei, largest producer), Iran (Nishapur), United States (Arizona, Nevada) | Merelani Hills, Tanzania (only commercial source) | Sri Lanka (Elahera), Australia (Harts Range), Myanmar, Vietnam, Cambodia |
| Wedding anniversary | 11th | 24th | Not listed |
| Added to U.S. list | Traditional | 2002 | 1952 |
| On UK list | Yes | Yes | No |
| Zodiac signs for December birthdays | Sagittarius (to about December 21) and Capricorn (from about December 22) | Same | Same |
Why does December have three birthstones?
Turquoise is the traditional December stone; zircon was added to the U.S. list in 1952 and tanzanite in 2002, giving December more color and durability options. June, August, and December are the three months with three birthstones; the full comparison is in the Birthstones by Month chart.
December birthstone colors
The December birthstone color is blue for all three stones: sky-blue to green turquoise, blue-violet tanzanite, and bright blue zircon. Zircon also occurs in colorless, red, orange, yellow, brown, and green. The table shows how each blue forms.
| Stone | Most prized color | Color origin |
|---|---|---|
| Turquoise | “Robin’s egg blue,” “sky blue,” “Persian blue” | Natural; often dyed or resin-stabilized |
| Tanzanite | Pure rich blue (valued above violet), with a “velvety” look | Heat treatment turns brownish zoisite blue-violet; the color is permanent |
| Zircon | Bright blue with strong fire | Usually heat-treated; blue and colorless zircon are mostly treated |
Zircon vs. cubic zirconia
Zircon is a natural zirconium silicate mineral; cubic zirconia is a synthetic zirconium oxide made in a laboratory as a diamond simulant. Only zircon is a December birthstone. The table separates them.
| Feature | Zircon (December birthstone) | Cubic zirconia |
|---|---|---|
| Origin | Natural mineral | Laboratory-made |
| Composition | Zirconium silicate | Zirconium oxide |
| Mohs hardness | 6–7.5 | About 8–8.5 |
| Colors | Blue, colorless, red, orange, yellow, brown, green | Any color |
| Birthstone status | Official December birthstone | Not a birthstone |
Tanzanite compared with other blue December birthstone look-alikes
| Feature | Tanzanite (December) | Blue sapphire (September) | Amethyst (February) |
|---|---|---|---|
| Mineral | Zoisite | Corundum | Quartz |
| Mohs hardness | 6–7 | 9 | 7 |
| Typical color | Blue-violet | Blue | Purple |
| Birthstone guide | This page | September Birthstone | February Birthstone |
December birthstone history
Turquoise has the longest history of the three December stones; tanzanite has the shortest. GIA records the following:
| Stone | History |
|---|---|
| Turquoise | Worn by ancient Egyptian pharaohs; carved by Chinese artisans more than 3,000 years ago |
| Turquoise | Mined in Iran’s Nishapur district for more than 1,000 years |
| Turquoise | A key gem in Native American cultures; the Apache associated it with rainbows |
| Zircon | Name possibly from the Arabic zarkun (cinnabar) or the Persian zargun (gold-colored) |
| Zircon | One of the nine gems of the Hindu navaratna; blue zircon was popular in Victorian jewelry of the 1880s |
| Tanzanite | Found in the Merelani Hills in 1967 and named after Tanzania; “one of the most exciting gem discoveries of the 20th century” |
| Tanzanite | Tiffany & Co. launched a major marketing campaign for it in 1968 |
Some natural zircon crystals from Western Australia’s Jack Hills have been dated to about 4.4 billion years old, among the oldest known pieces of Earth’s crust.
Folklore held that turquoise guaranteed “health and good fortune” and that zircon could “lull one into a deep sleep and scare off evil spirits”; these beliefs describe tradition, not gemological properties.
Choosing and caring for a December birthstone
None of the December birthstones is as hard as sapphire, so each suits some jewelry better than others. Zircon and tanzanite are the more durable choices for rings with protective settings; turquoise suits pendants, earrings and bead jewelry. GIA gives these care rules:
- Turquoise: clean only with warm, soapy water; never use steam or ultrasonic cleaners. Keep it away from heat, acids, cosmetics, skin oils and perspiration, which can discolor it. Treated surfaces can be damaged by heat or solvents (GIA turquoise care).
- Tanzanite: warm, soapy water is always safe; “ultrasonic and steam cleaners are never recommended.” Avoid hard blows, extreme heat and sudden temperature changes (GIA tanzanite care).
- Zircon: clean with warm, soapy water and a soft brush; no ultrasonic or steam cleaners. Store it separately, because zircon is brittle and its facet edges wear against other jewelry (GIA zircon care).
- Heat-treated zircon: keep it out of prolonged bright light, which can make some stones fade back to light brown.
What the December birthstone is not
The December birthstones are often misunderstood. The points below separate the facts.
- Zircon is not cubic zirconia. One is a natural mineral, the other a synthetic simulant.
- Tanzanite is not sapphire. It is a softer zoisite with a blue-violet color.
- Turquoise is not transparent. It is semi-translucent to opaque.
- December does not have only one birthstone. Turquoise, tanzanite, and zircon are all official in the U.S.
Frequently asked questions
What color is the December birthstone?
The December birthstone color is blue: turquoise is sky blue to green, tanzanite blue-violet and zircon bright blue, though zircon also occurs in other colors.
Where does tanzanite come from?
Tanzanite comes from a single commercial source, the Merelani Hills of northern Tanzania, where it was found in 1967.
Is zircon the same as cubic zirconia?
No. Zircon is a natural mineral and an official December birthstone; cubic zirconia is a synthetic diamond simulant.
