December is one of the most gem-rich birth months: tanzanite, blue topaz, turquoise, and zircon, four stones with distinctly different personalities. This article focuses on the two principal stones: tanzanite, a rare and relatively recent gem with a singular blue-violet hue, and blue topaz, radiant and wonderfully accessible.
Tanzanite is the youngest of the great jewellery gemstones, discovered as recently as 1967. Blue topaz, known since Antiquity, had its modern story transformed by irradiation, a treatment that revolutionized its accessibility. Gifting a December birthstone for Christmas combines personal symbolism with the magic of the festive season: a gift that carries a double meaning.
What are the birthstones of December?
December has four official birthstones:
- Tanzanite: a blue-violet variety of zoisite, discovered in 1967 in Tanzania. The most recent and the rarest of the great gemstones.
- Blue topaz: an aluminium fluorosilicate, available in three shades (Sky Blue, Swiss Blue, London Blue). The most accessible of the four.
- Turquoise: an opaque blue-green stone used for over 5,000 years. December's historic birthstone, predating tanzanite.
- Zircon: not to be confused with cubic zirconia (CZ). Blue zircon is a natural mineral of exceptional brilliance.
Why four stones? The original 1912 list (American National Retail Jewelers Association) included turquoise and zircon. Tanzanite was added in 2002 by the AGTA as the first new birthstone since 1912.
Tanzanite: discovery, history, and exceptional rarity
1967, the discovery. Manuel d'Souza, a Maasai prospector, discovers blue-violet crystals in the hills of Merelani, near Arusha, Tanzania. According to legend, a shepherd had noticed blue crystals among stones exposed by a bush fire. D'Souza initially mistakes them for sapphires.
1968, the naming by Tiffany. Henry Platt, Vice President of Tiffany & Co, recognizes the commercial potential of this new gemstone. He names it "tanzanite" as a tribute to its country of origin. Tiffany becomes the first major jeweller to bring it to market.
Tanzanite is sourced exclusively from the Merelani Hills, within an area of approximately 20 square kilometres. It is the only major gemstone in the world with a single geographical source. Certain geological reports (TanzaniteOne, USGS) suggest that reserves could be exhausted within 20 to 30 years. This rarity gives tanzanite a growing significance as a heritage stone.
From a mineralogical standpoint, tanzanite is a variety of zoisite coloured by vanadium. In its rough state, it is often brownish: it is the heat treatment (around 600°C) that reveals its signature blue-violet colour.
To learn more, consult the full profile from the GIA on tanzanite.
The trichroism of tanzanite: a stone that changes color
Tanzanite is trichroic: it displays three distinct colours depending on the viewing angle, blue, violet, and burgundy (reddish-brown). This is one of the most spectacular optical phenomena in the world of gemology.
Sapphire, by comparison, is dichroic (two colours). Tanzanite goes further, exhibiting three distinct colours within a single stone. This is a fascinating property that Mayuri clients often discover when turning the stone under different angles.
Gem cutters orient the stone to maximise either the blue or the violet. The most prized tanzanites display an intense blue with a violet shimmer, the coveted "tanzanite blue." This phenomenon cannot be captured in photographs: it reveals itself in hand, under varying light sources.
Blue topaz: London Blue, Swiss Blue, and Sky Blue
Natural topaz is most often colourless or pale. The rich blue colour we know is achieved through irradiation (neutrons or electrons) followed by heat treatment. This treatment is stable, permanent, and universally accepted within the trade.
Three distinct shades define the market:
| Variety | Colour | Saturation | Indicative Price (ct) |
|---|
| Sky Blue | Pale sky blue | Light | $6-18 |
| Swiss Blue | Vivid, electric blue | Medium | $12-30 |
| London Blue | Deep blue, blue-grey | Intense | $18-36 |
London Blue is the most sought-after in fine jewellery. Its deep blue with grey undertones evokes sapphire at a fraction of the price. Worth noting: imperial topaz (orange to pink, untreated, from Ouro Preto in Brazil) is the only variety of topaz that is naturally coloured with significant value. The vast majority of blue topazes on the market are treated; this is the norm, not the exception.
For a deeper dive, explore the full guide from GIA on topaz.
Turquoise and zircon: the other birthstones of December
Turquoise. A copper and aluminium phosphate, used for over 5,000 years (ancient Egypt, pre-Columbian civilisations). An opaque blue-green stone, instantly recognisable. Sleeping Beauty turquoise (Arizona) and Persian turquoise (Iran) are the most prized. Hardness 5 to 6 on the Mohs scale, delicate and sensitive to chemicals.
Zircon. Not to be confused with cubic zirconia (CZ, a diamond simulant). Zircon is a natural mineral (ZrSiO4) whose blue variety is prized in fine jewellery for its remarkable brilliance and dispersion. It is one of the oldest terrestrial minerals: certain zircon crystals date back 4.4 billion years.
For a piece featuring turquoise or zircon, Mayuri can source these stones as part of a bespoke project.
Comparative gemological properties
| Property | Tanzanite | Blue Topaz | Turquoise | Zircon |
|---|
| Composition | Zoisite (Ca2Al3(SiO4)3(OH)) | Al2SiO4(F, OH)2 | CuAl6(PO4)4(OH)8·4H2O | ZrSiO4 |
| Mohs Hardness | 6-7 | 8 | 5-6 | 6-7.5 |
| Optical phenomenon | Trichroism | None | None | Strong dispersion |
| Common treatment | Heating (~600°C) | Irradiation + heating | Stabilisation / waxing | Heating |
| Colour | Blue-violet | Blue (3 shades) | Opaque blue-green | Blue, colourless |
| Indicative price (ct) | $240-$950 | $6-$35 | $2-$60 | $35-$180 |
| Main origin | Tanzania (unique) | Brazil, Nigeria, Sri Lanka | Iran, USA, China | Cambodia, Sri Lanka |
A highly sought-after comparison that remains almost entirely absent from French-language content.
Color. Tanzanite is blue-violet with warm undertones and violet shimmer. Blue Sapphire is a pure blue, sometimes with velvety reflections (cornflower blue). Tanzanite shifts color depending on the angle (trichroism), while Sapphire remains more stable.
Hardness. Sapphire rates 9 on the Mohs scale, compared to tanzanite's 6-7. Sapphire is far more resistant to scratches and impact, making it ideal for rings worn daily. Tanzanite is better suited to Earrings, pendants, and occasional rings.
Price. For equivalent color quality, tanzanite is significantly more accessible. An intense blue tanzanite of 1 ct: $475-$950. A blue Sapphire of the same saturation: $1,200-$6,000.
Future rarity. Tanzanite reserves are finite (20-30 years). Sapphire is mined across multiple countries (Sri Lanka, Madagascar, Myanmar, Australia). Tanzanite could become even rarer and more precious over time.
Virtues and benefits of tanzanite and blue topaz
In crystal healing, tanzanite is associated with the third eye chakra and the crown chakra. Traditionally linked to spiritual awakening, inner transformation, and communication, it is prized in meditation for its connection to intuition and clairvoyance. Tanzanite is also regarded as a stone of transition and change. Blue topaz is associated with the throat chakra. Traditionally linked to communication, serenity, and creativity, it is renowned for
soothing tension and encouraging self-expression. Tanzanite: Commercial quality (pale lavender, visible inclusions): $120-$350/ct
Price guide: tanzanite and blue topaz in fine jewellery
Tanzanite:
- Commercial quality (pale lavender, visible inclusions): $120-$350/ct
- Good quality (medium blue-violet, eye-clean): $350-$950/ct
- Exceptional quality (intense blue, rated "exceptional" on the TanzaniteOne scale): above $1,200/ct
- Stones above 5 ct of exceptional quality are rare and reach $2,400-$3,600/ct
Blue topaz:
- Sky Blue: $6-$18/ct
- Swiss Blue: $12-$30/ct
- London Blue: $18–35/ct
- Blue topaz is one of the most accessible gemstones, ideal as a first coloured stone piece
Tanzanite and blue topaz span a wide range of budgets, from the accessible (blue topaz) to the exceptional (top-quality tanzanite). Contact Mayuri for a personalised quote tailored to your project.
Caring for your tanzanite and blue topaz jewellery
Tanzanite (6–7 on the Mohs scale), more delicate than Sapphire or Emerald:
- Sensitive to thermal shock: avoid moving it abruptly from very hot to very cold environments
- Clean with lukewarm soapy water and a soft cloth only. Never use ultrasonic or steam cleaners (risk of fracturing)
- Remove before sport, manual work, and gardening
- Store separately from harder stones (Diamond, Sapphire) to prevent scratching
- Ideal for: Earrings, pendants, occasional rings
Blue topaz (8 on the Mohs scale), more resilient:
- Good hardness, yet sensitive to sharp impacts due to its perfect cleavage in one direction
- Clean with lukewarm soapy water and a soft cloth. Ultrasonic cleaning is possible unless the stone contains inclusions
- Avoid prolonged exposure to extreme heat, as discolouration is possible, though rare in treated topazes
- Suitable for everyday wear, including as a ring
Recommended routine: wipe after each wear, full cleaning once a month.
Gifting a December birthstone for Christmas: a gift guide
December offers the strongest seasonal potential of the entire series: December birthdays and Christmas gifts combine beautifully.
Tanzanite, the premium gift. Rare and sophisticated, a tanzanite piece says "I chose a stone few people know, just for you." Its blue-violet hue resembles no other gemstone.
Blue topaz, the radiant gift. Accessible and versatile, London Blue delivers a deep, elegant hue, while Swiss Blue offers a vivid, contemporary brilliance.
Personalisation. A jewel featuring the recipient's birthstone adds a symbolic and personal dimension to the gift. Christmas is the perfect occasion to offer a bespoke piece of jewellery set with a birthstone; simply plan ahead to allow time for creation.
Create your bespoke jewel with Mayuri
Our atelier crafts bespoke jewellery in 18K yellow gold with tanzanite or blue topaz. Contact our team to bring your project to life: selecting the stone, the setting, and the metal.
Tanzanite and blue topaz pair beautifully with 18K white gold, whose cool brilliance enhances their blue hues, as well as with 18K yellow gold for a warm contrast and a timeless effect. This is a personalised Christmas gift that combines rarity, colour, and craftsmanship.
Frequently asked questions
What is the birthstone for December?
December has four official birthstones: tanzanite, blue topaz, turquoise, and zircon. Tanzanite and blue topaz are the most popular in contemporary fine jewellery. Turquoise is the historic birthstone of December, cherished since Antiquity. Blue zircon (not to be confused with cubic zirconia) is a natural mineral with a remarkable brilliance.
Why does December have several birthstones?
The original 1912 list associated turquoise and zircon with December. Tanzanite was added in 2002 by the American Gem Trade Association (AGTA), marking the first new birthstone addition since the list was established. Blue topaz was later introduced as an accessible alternative. December and June are the two months with the greatest number of alternative birthstones.
What is the difference between tanzanite and Sapphire?
Tanzanite is blue-violet with a spectacular trichroism, displaying three colours depending on the viewing angle. Sapphire offers a purer, more stable blue. Sapphire is considerably harder, 9 versus 6 to 7 on the Mohs scale, making it better suited to everyday rings. At equivalent colour quality, tanzanite is more accessible: $350 to $950 per carat, compared to $1,200 to $6,000 per carat for blue sapphire.
What is the price of a tanzanite?
Prices vary according to colour, clarity, and carat weight. Commercial quality, pale lavender: $120 to $350 per carat. Good quality, medium blue-violet: $350 to $950 per carat. Exceptional quality, intense blue over one carat: $1,200 to $3,600 per carat. The budget for a tanzanite piece in 18K gold varies depending on stone quality and setting complexity; contact Mayuri for a personalised quote.
Is tanzanite rare?
Yes, tanzanite is exceptionally rare. It is found in only one location in the world: the Merelani Hills of Tanzania, within an area of just 20 square kilometres. Some experts estimate that reserves could be exhausted within 20 to 30 years. It is the only major gemstone in fine jewellery with a single geographic source.
What is London Blue topaz?
London Blue is the deepest variety of blue topaz, with a rich blue that leans toward a grey-blue tone. It is produced through neutron irradiation followed by heat treatment of a colourless topaz. Its blue is reminiscent of sapphire, at a fraction of the price, ranging from $18 to $36 per carat. It is the most sought-after shade in fine jewellery.
How do you care for a tanzanite jewel?
Tanzanite has a hardness of 6 to 7 on the Mohs scale, making it more delicate than sapphire or diamond. Clean with lukewarm soapy water and a soft cloth. Avoid ultrasonic cleaners, steam, and thermal shock entirely. Remove your jewellery before sport or manual work. Tanzanite is ideally suited to Earrings and pendants, or to rings worn on special occasions.
What are the virtues of tanzanite?
In crystal healing, tanzanite is associated with the third eye chakra and the crown chakra. It is traditionally linked to spiritual awakening, inner transformation, and intuitive communication.
What is the difference between blue topaz and aquamarine?
Blue topaz, which is typically treated, is more accessible, ranging from $6 to $36 per carat, and is available in three shades: Sky, Swiss, and London. Aquamarine is naturally blue, requiring no treatment, and offers a more delicate, pastel hue. Aquamarine, rated 7.5 to 8 on the Mohs scale, and blue topaz, rated 8, have comparable hardness. Those born in March claim aquamarine as their birthstone, while those born in December have blue topaz.
