December holds the distinction of having three official birthstones: turquoise, zircon, and tanzanite. Turquoise is one of the oldest gemstones used in jewelry, dating back thousands of years. Zircon is a naturally occurring gemstone often confused with synthetic cubic zirconia, despite being an entirely different mineral. Tanzanite is the newest of the three, discovered in 1967 and found in only one place on Earth.
This guide covers the mineralogy, history, and buying considerations for all three gems.
Turquoise: The Science Behind an Ancient Gem
Turquoise is a hydrated phosphate mineral containing copper and aluminum, which is responsible for its signature blue-to-green color. Copper produces the blue tones, while iron impurities shift the color toward green. Unlike faceted gemstones, turquoise is opaque and typically cut into cabochons, smooth domed shapes that highlight its color and matrix pattern rather than brilliance.
On the Mohs hardness scale, turquoise ranks between 5 and 6, making it relatively soft and porous compared to gems like sapphire or topaz. Its porosity means it can absorb oils, lotions, and even color from skin contact over time, which affects how it should be worn and cared for.
Turquoise Matrix Patterns
Many turquoise stones display a matrix, a web-like pattern of the host rock left behind during formation. Buyers generally fall into two camps:
- Matrix-free turquoise: Solid, uniform color, considered higher grade in most commercial markets
- Spiderweb turquoise: Visible matrix veining, prized in Southwestern and artisan jewelry traditions for its natural character
At Fascinating Diamonds, turquoise pieces are lab-grown, replicating the same mineral composition and color consistency while avoiding the porosity concerns of natural, untreated turquoise. Browse our full gemstone jewelry collection to explore turquoise alongside other birthstone options.
Zircon: The Science Behind a Misunderstood Gem
Zircon is a naturally occurring zirconium silicate mineral, chemically and structurally unrelated to cubic zirconia, which is a synthetic material invented in the 1970s as a diamond simulant. This naming coincidence has caused decades of confusion, but zircon has been mined and used in jewelry for thousands of years, making it one of the oldest gem minerals on Earth, with some zircon crystals dated at over 4 billion years old.
Zircon occurs naturally in a range of colors, including blue, yellow, brown, green, and red, caused by trace elements and internal structural variations. Most blue zircon on the market is the result of heat-treating brown zircon, a process that has been used since the early 20th century.
On the Mohs scale, zircon ranks 6 to 7.5, with harder, more heat-treated stones typically ranking toward the higher end. Zircon also has an unusually high refractive index for a natural gemstone, giving it a brilliance and fire that rivals diamond, which is part of why it was historically used as a diamond substitute before cubic zirconia and moissanite existed.
Tanzanite: The Science Behind a Single-Source Gem
Tanzanite is a blue-to-violet variety of the mineral zoisite, discovered in 1967 in the Merelani Hills near Mount Kilimanjaro in Tanzania. It remains the only place on Earth where gem-quality tanzanite has been found, making it geologically rarer than diamond by several estimates.
Tanzanite's color comes from trace vanadium within the crystal structure, and most tanzanite on the market has been heat-treated to enhance its blue-violet saturation, a process that also removes brownish undertones present in the untreated stone. The gem displays strong pleochroism, meaning it shows different colors, typically blue, violet, and burgundy, depending on the angle it's viewed from, which is why cutting orientation significantly affects the final face-up color.
On the Mohs scale, tanzanite ranks 6 to 7, making it more fragile than sapphire or topaz and better suited to jewelry that avoids daily impact.
History and Symbolism
Turquoise has been used in jewelry for over 6,000 years, with archaeological evidence tracing its use to ancient Egypt, Persia, and pre-Columbian Central America. It has long been associated with protection, healing, and good fortune, and it holds particular cultural significance in Native American, particularly Navajo and Zuni, jewelry traditions.
Zircon appears in historical texts and religious writings dating back to the Middle Ages, where it was associated with wisdom, honor, and protection during travel. Its brilliance led to frequent confusion with diamond throughout history, long before its molecular difference from diamond was understood.
Tanzanite was added to the official birthstone list in 2002 by the American Gem Trade Association, the first change to the list since 1912, reflecting its rapid rise in popularity following its discovery. Tiffany & Co. played a major role in its early marketing, naming the stone after its country of origin to distinguish it from the mineral zoisite, whose name was seen as unmarketable.
Choosing Among Turquoise, Zircon, and Tanzanite
With three official options, the decision often comes down to color preference, durability needs, and rarity.
Turquoise is a better fit when:
- A distinctive opaque blue-green color and matrix pattern is desired
- The piece draws on Southwestern or artisan-style design traditions
- The item will be worn occasionally rather than daily, given its softness and porosity — pendants and earrings are ideal formats
Zircon is a better fit when:
- High brilliance and fire at an accessible price point are priorities
- A faceted, diamond-like appearance is preferred over an opaque stone
- The wearer wants a gem with genuine historical rarity that is often mistaken for a synthetic
Tanzanite is a better fit when:
- A rich blue-violet color is the priority
- The wearer values single-source rarity
- The piece will be worn with reasonable care, avoiding daily high-impact wear
How to Choose a Piece
For Turquoise
- Color consistency: Even, saturated blue or blue-green tone is generally preferred, though matrix patterns are valued in artisan styles.
- Porosity: Ask whether the stone has been stabilized, a common treatment that fills natural pores with resin to improve durability.
- Setting: Bezel settings are recommended to protect turquoise's edges given its softness.
For Zircon
- Color: Blue is the most popular commercial color, though natural earth tones are gaining interest among buyers seeking untreated stones.
- Cut: Because zircon is brittle at its facet edges, a well-executed cut with protected edges reduces the risk of chipping.
- Clarity: Zircon typically forms with good clarity, and eye-clean stones are standard for jewelry-grade pieces.
For Tanzanite
- Color saturation: Deep blue-violet with minimal gray or brown undertone is the most valued combination.
- Cut orientation: Because of tanzanite's pleochroism, the cutter's choice of orientation determines whether the stone reads more blue or more violet face-up.
- Setting: Protective settings such as bezel or halo are recommended given tanzanite's moderate hardness.
Caring for December Birthstone Jewelry
Turquoise:
- Avoid water, oils, lotions, and perfume, all of which can be absorbed by its porous structure.
- Clean only with a soft, dry cloth.
- Remove before swimming, showering, or applying skincare products.
Zircon:
- Clean with warm water and mild soap.
- Avoid knocking facet edges against hard surfaces, since zircon can chip more easily than harder gems.
- Store separately to avoid surface abrasion from harder stones like diamond.
Tanzanite:
- Clean with warm water and a soft brush, avoiding ultrasonic and steam cleaners.
- Avoid extreme temperature changes, which can cause internal fracturing.
- Remove before activities involving impact, given its moderate hardness.
Real Customer Reviews
Frequently Asked Questions
Why does December have three birthstones?
Turquoise and zircon were both included in the original 1912 birthstone list. Tanzanite was added in 2002 by the American Gem Trade Association, the first update to the list in 90 years, giving December buyers three distinct options
Is zircon the same as cubic zirconia?
No. Zircon is a naturally occurring mineral that has existed for billions of years, while cubic zirconia is a synthetic material first produced in the 1970s. They share a similar name but are chemically unrelated.
Why is tanzanite only found in one place?
Tanzanite forms under a very specific set of geological conditions that have so far only been identified in the Merelani Hills near Mount Kilimanjaro in Tanzania, making it geologically rarer than diamond.
Is turquoise durable enough for daily wear?
Turquoise ranks 5 to 6 on the Mohs hardness scale and is porous, making it less suited to daily wear rings than harder gems. It performs better in earrings, pendants, or occasional-wear pieces.
What makes tanzanite change color depending on the angle?
Tanzanite displays pleochroism, a property that causes it to show different colors, typically blue, violet, and burgundy, depending on the viewing angle. Cutters orient the stone to emphasize the most desirable face-up color.