December has three birthstones: tanzanite, turquoise and zircon (usually the blue kind). All three are blue, but they are very different stones. Tanzanite is a faceted violet-blue gem from a single small mining area in Tanzania. Turquoise is an opaque sky-blue to green stone that is usually treated. Blue zircon is a bright, sparkly natural gem that a lot of shoppers mix up with cubic zirconia. Each one has its own treatments, durability and care, so it helps to know which one you are buying before you compare settings.
This guide covers what each December birthstone is, how hard it is, the treatments that are normal (and the ones that should be disclosed), how to read a jewelry listing, and how to care for each stone. It ends with a buying checklist and seven sterling-silver pieces we checked live today. If you are shopping for a November birthday instead, see our November birthstones guide to topaz and citrine.
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December’s three birthstones at a glance
- Tanzanite is the blue-to-violet variety of the mineral zoisite, measuring 6 to 7 on the Mohs hardness scale. It is mined commercially only in the Merelani Hills of northern Tanzania, in the shadow of Mount Kilimanjaro. According to GIA, most tanzanite starts out brownish and is heat treated to get its blue-violet color, and that color is permanent.
- Turquoise is an opaque copper-aluminum phosphate, measuring 5 to 6 on the Mohs scale, so it is the softest of the three. Its color runs from sky blue to green, sometimes with dark veins of host rock called matrix. A lot of the turquoise sold today is treated to improve durability or color.
- Zircon is a natural silicate gem measuring 6 to 7.5 on the Mohs scale. It has strong brilliance and fire, which is why blue zircon looks so lively. GIA notes that zircon is commonly heat treated to produce blue and colorless stones. Zircon is not cubic zirconia. Cubic zirconia (CZ) is a lab-made material with a similar name, and that’s all they have in common.
- What about blue topaz? Some retailers market blue topaz as a December stone, and you’ll often see it in December gift lists. It isn’t on GIA’s or the American Gem Society’s December lists, which name tanzanite, zircon and turquoise. If your December person simply loves blue, topaz is a durable choice; we cover it in our November guide.
Tanzanite: what to look for
- Color is the main value factor. Tanzanite ranges from lavender to deep violet-blue. Stronger, more saturated color usually costs more. Paler stones are pretty and more affordable, but they can look washed out in a small size.
- It shifts color with the angle. Tanzanite is strongly pleochroic, meaning it shows different shades of blue, violet and sometimes a hint of burgundy depending on how you look at it. That’s normal, and part of its appeal.
- Heat treatment is standard. Expect it. A listing that says “heat-treated tanzanite” is being transparent, not warning you off. Other treatments, such as coatings, are less common and should be disclosed.
- Treat it gently. At 6 to 7 on the Mohs scale, tanzanite can scratch and chip more easily than sapphire. GIA notes it can crack with sudden temperature changes. It is best in earrings and pendants. Rings are fine for careful or occasional wear, ideally in a protective setting.
Turquoise: natural, stabilized, reconstituted or imitation
Turquoise listings use a handful of terms that matter more than the shade of blue. Here is what they mean in plain terms.
- Natural (untreated) turquoise is cut and polished with nothing added. Hard, high-quality untreated material is relatively scarce and usually priced accordingly. If a seller claims it, they should say so clearly.
- Stabilized turquoise is real turquoise that has been impregnated with a clear resin (such as epoxy or acrylic) to make a porous stone harder, more durable and better at holding a polish. It is very common and perfectly fine to buy, as long as it is labeled. GIA’s turquoise page covers these treatments in more detail.
- Dyed turquoise has had its color added or deepened. It is often combined with stabilizing. It should be disclosed.
- Reconstituted (or “block”) turquoise is made from turquoise chips or powder bonded with resin into a block, then cut. It contains real turquoise, but it is not a solid stone. It is much less valuable than solid turquoise and should be labeled as reconstituted.
- Imitations are other materials made to look like turquoise, most often dyed howlite or magnesite, glass or plastic. Words like “turquoise-color,” “turquoise-tone” or a very low price on a large, perfectly uniform stone are a reason to read the specs.
- Mine names such as Sleeping Beauty or Kingman (both in Arizona) describe where turquoise came from. They help you understand the look, but they don’t tell you on their own whether the stone was treated.
Blue zircon: what to look for
- Brightness and fire. Zircon has a high refractive index and strong dispersion, so a well-cut stone throws off bright flashes of light. The best blue zircon is a vivid, slightly greenish to pure blue.
- Heat treatment is standard here too. Almost all blue zircon gets its color from heating. GIA notes that some heat-treated zircon can slowly revert toward its original brownish color with long exposure to strong light. Don’t leave it on a sunny windowsill for weeks.
- Facet edges can wear. Zircon is reasonably hard, but it is brittle, so facet edges can chip or abrade if stones knock against each other. Store zircon separately, and pick earrings or pendants for daily wear.
- Read “zircon” carefully. “Blue zircon” or “natural zircon” means the real gem. “Cubic zirconia,” “CZ” or “zirconia” means the lab-made simulant. Some listings use both, for example a natural blue zircon with tiny white CZ accents.
How to read a December birthstone listing
- Find the stone type and the treatment line. Good listings say things like “heat-treated tanzanite,” “stabilized turquoise” or “natural blue zircon, heat treated.” If a listing says nothing about treatment, assume the standard treatment for that gem: heat for tanzanite and zircon, stabilization for most turquoise.
- Check for conflicting details. Marketplace listings sometimes say one thing in the title and another in the spec table. When they disagree, go by the most specific statement (usually the description or the stone-information table), or ask the seller before buying.
- Look at size in millimeters, not just carats. Carat weight is a weight, and zircon is a dense stone, so a 1-carat zircon looks smaller than a 1-carat tanzanite. Millimeter size tells you how big the stone will actually look.
- Note the metal. Sterling silver (stamped 925) is affordable and easy to wear. Gold-plated silver can wear through with time. Solid gold costs more but lasts longest.
- For rings, pick your size. Ring listings are usually variation listings. Select the size you need before adding to the cart, and choose a setting that protects softer stones.
A buying checklist
- Decide which December stone suits the person: deep violet-blue sparkle (tanzanite), opaque Southwestern or boho blue (turquoise), or bright icy-blue sparkle (blue zircon).
- Confirm the treatment is disclosed: heat treated, stabilized, dyed or reconstituted.
- Match the stone to the wear: earrings and pendants for tanzanite, turquoise and zircon; rings only for careful wearers or occasional wear.
- Check the millimeter size and the chain length; an 18-inch chain sits just below the collarbone.
- Confirm the metal (925 sterling, plated or solid gold) and the earring back or clasp type.
- Check the return window, especially for color-sensitive stones like tanzanite, whose color looks different in daylight and indoors.
- Want to layer a birthstone pendant or stack a birthstone ring? See how to layer necklaces and how to stack rings.
Our picks
These listings were checked live today. Links go straight to Amazon with our Associates tag. We don’t list prices here, so check the product page for the current offer. Each description below is based only on what the listing itself states, including the treatment wording.
1. Gem Stone King 925 Sterling Silver Tanzanite Pendant Necklace (Oval 8×6 mm, 1.30 cttw)
A single oval 8×6 mm tanzanite, listed at 1.30 carats total weight, set in 925 sterling silver and sold with an 18-inch sterling silver cable chain with a spring-ring clasp. The listing describes the color as blue-violet. It does not spell out a treatment, but as GIA notes, almost all tanzanite on the market is heat treated, so assume this one is. A pendant is the easiest way to wear tanzanite, because it is protected from knocks.
Best for: a classic December birthstone necklace for everyday wear
2. Ross-Simons 2.10 ct. t.w. Tanzanite Flower Earrings in Sterling Silver
Flower-shaped studs made of oval and round tanzanites, listed at 2.10 carats total weight, in polished sterling silver with post/clutch backs. Each earring is about 1/2 inch across. The product description lists the stones as natural and heat-treated. (One spec field says “not treated”; we are going by the more detailed description, which matches standard practice for tanzanite.) Ross-Simons notes that the natural stones may show inclusions and color variation.
Best for: a statement tanzanite earring for holiday parties or a milestone December birthday
3. Gem Stone King 925 Sterling Silver Tanzanite Ring (1.16 ct Oval 8×6 mm)
A prong-set oval 8×6 mm tanzanite solitaire, listed at 1.16 carats and described as heat-treated blue tanzanite, in 925 sterling silver. The page may open on size 8; the listing offers sizes 5 through 9, so select your ring size before you add it to the cart. Since tanzanite is 6 to 7 on the Mohs scale, this is best as a dress ring or for careful daily wear. Take it off for workouts, gardening and cleaning.
Best for: a December birthday ring for someone who will baby it a little
4. Timberline Traders Sleeping Beauty Turquoise Stud Earrings, 8 mm, 925 Sterling Silver
Small 8 mm turquoise studs in 925 sterling silver with push backs. The listing says they are handmade in small batches by Navajo artisans in New Mexico and that the stone is Sleeping Beauty turquoise from Globe, Arizona, a mine the seller notes closed in 2012. Sleeping Beauty turquoise is known for its even sky-blue color with little or no matrix. The listing does not say whether the turquoise is stabilized, and much commercial turquoise is, so ask the seller if that matters to you.
Best for: a small, wearable turquoise stud with a clear origin story
5. Ross-Simons Marquise Turquoise Pendant Necklace in Sterling Silver
This is a mosaic of treated turquoise, not a single solid stone. The product description describes an 18×35 mm marquise cabochon mosaic of stabilized turquoise with colorful shell pieces and added copper to create a matrix effect. It lists the turquoise treatment as dyed and stabilized. It hangs on an oxidized sterling silver popcorn chain from Italy with a lobster clasp. The listing offers 18- and 20-inch lengths, so choose the length you want. It’s an honest, bold turquoise look, and the treatments are disclosed up front.
Best for: a boho or Southwestern statement pendant
6. Gem Stone King 925 Sterling Silver Blue Zircon Pendant Necklace (Round 6 mm, 1.20 cttw)
A round 6 mm heat-treated natural blue zircon, listed at 1.20 carats, prong-set in 925 sterling silver and sold with an 18-inch cable chain with a spring-ring clasp. This is genuine zircon, not cubic zirconia. Zircon’s high brilliance makes even a 6 mm stone look bright, and a pendant keeps its facet edges away from knocks.
Best for: an icy-blue December pendant with lots of sparkle
7. Gem Stone King Blue Zircon Bezel Stud Earrings, 925 Sterling Silver (Oval 7×5 mm, 2.50 cttw)
A pair of oval 7×5 mm heat-treated natural blue zircons, listed at 2.50 carats total weight, in bezel settings of 925 sterling silver with post and friction backs. A bezel (a rim of metal around the stone) is a smart choice for zircon, because it protects the facet edges that can chip in open prongs.
Best for: everyday blue zircon studs that are protected from knocks
Caring for December birthstones
- Tanzanite: clean with warm, soapy water and a soft brush. Skip ultrasonic and steam cleaners, avoid sudden temperature changes and store it away from harder gems that can scratch it.
- Turquoise: wipe it with a soft, slightly damp cloth, or use warm soapy water if needed. Never use ultrasonic or steam cleaners, solvents or jewelry dips. Put it on after lotion, perfume and sunscreen, since GIA notes that cosmetics and even skin oils can discolor turquoise over time.
- Blue zircon: clean with a soft brush and mild soap in warm water; GIA advises against ultrasonic and steam cleaners for zircon. Because zircon tends to abrade, take it off for gardening, sports and dishes, store each piece separately, and keep it out of long, strong sun exposure.
- Sterling silver: it tarnishes naturally. Store pieces in a pouch or a closed box, and polish with a silver cloth, avoiding the turquoise itself.
Want more detail on any of these gems? GIA’s pages on tanzanite, turquoise and zircon cover properties, treatments and sources.
Quick answers
What is the birthstone for December?
December has three official birthstones: tanzanite, turquoise and zircon, usually blue zircon. Blue topaz is also sold as a December stone by some retailers, but it isn’t on the GIA or AGS December lists.
Which December birthstone is the most durable?
Blue zircon is the hardest at 6 to 7.5 on the Mohs scale, though it is brittle at the facet edges. Tanzanite is 6 to 7 and turquoise is 5 to 6. For everyday wear, earrings and pendants are the safest choice for all three.
Is tanzanite always heat treated?
Almost always. Most tanzanite is mined as brownish zoisite and heated to get its blue-violet color. The result is permanent and is standard practice in the trade.
Is stabilized turquoise real turquoise?
Yes. Stabilized turquoise is real turquoise impregnated with clear resin so it is harder and more durable. Reconstituted turquoise is made from bonded turquoise powder or chips, and imitations such as dyed howlite are not turquoise at all.
Is blue zircon the same as cubic zirconia?
No. Zircon is a natural gemstone, a zirconium silicate. Cubic zirconia is a lab-made material, a zirconium oxide, that is used as a diamond simulant. The names are similar, but they are different things.
Can you wear a tanzanite ring every day?
You can, but it needs care. Tanzanite scratches and chips more easily than sapphire, so choose a protective setting and take it off for sports, cleaning and other hands-on work.
How do I clean turquoise jewelry?
Wipe it with a soft, damp cloth, or use warm soapy water if needed. Avoid ultrasonic and steam cleaners, solvents and jewelry dips, which can damage turquoise and its treatments.