For those born in the final month of the year, the privilege of selecting a birthstone is uniquely abundant. Unlike months with a single gem, December offers a vibrant palette of blue, represented by three distinct stones: Tanzanite, Turquoise, and Zircon. These gems, ranging from the ancient earth-mined turquoise to the recently discovered tanzanite and the brilliant zircon, collectively symbolize wisdom, protection, and spiritual growth. While historical and modern lists may vary, the current consensus among major jewelry authorities recognizes this "blue trio" as the definitive birthstones for December. This guide explores the geological origins, gemological properties, historical lore, and practical care of these three magnificent gemstones.
The Historical Evolution of December’s Gems
The concept of birthstones has evolved significantly over centuries, rooted in biblical texts and ancient traditions. The Breastplate of Aaron, described in the Book of Exodus, was set with twelve gemstones representing the twelve tribes of Israel. By the 1st century, historian Josephus drew a connection between these twelve stones and the twelve signs of the zodiac, suggesting that wearing a specific gem during its corresponding month amplified its powers. This eventually led to the tradition of wearing all twelve stones throughout the year for maximum benefit.
The modern list of birthstones, however, is largely attributed to the National Association of Jewelers (now Jewelers of America), which standardized a list in 1912. This list has been updated occasionally to reflect availability and trends. Turquoise has long been associated with December, likely due to its sky-blue color reminiscent of winter skies. Zircon was added to the list to provide a durable, brilliant alternative. Tanzanite, a 20th-century discovery, was officially added to the December list in 2002, acknowledging its rapid rise in popularity and cultural significance.
It is important to note that sources offer some variation in historical lists. Some older traditions or specific cultural interpretations may include Blue Topaz or Lapis Lazuli as December stones. However, the prevailing contemporary standard, recognized by the major trade organizations and reflected in the majority of gemological literature, settles on the trio of Tanzanite, Turquoise, and Zircon.
Tanzanite: The Gem of a Century
Geological Formation and Sources Tanzanite is a relative newcomer to the gem world, both geologically and historically. It is a variety of the mineral zoisite and owes its existence to a unique geological event that occurred roughly 585 million years ago. During the metamorphism of the East African Orogeny, intense heat and pressure altered the host rocks, infusing them with the elements necessary to form zoisite. The specific trace elements that cause tanzanite’s signature blue (vanadium) and purple (chromium) hues are found only in a small, four-square-kilometer mining area in the Merelani Hills of Northern Tanzania, near the majestic Mount Kilimanjaro. This extreme rarity—mined in a single location on Earth—makes tanzanite significantly rarer than diamond, ruby, sapphire, or emerald.
Gemological Properties Tanzanite is renowned for its trichroism, a pleochroic property where the stone displays three different colors when viewed from three different crystallographic directions: blue, violet, and burgundy (or red). Master cutters orient the rough stone to display the dominant blue-violet face-up color, though the secondary flashes of red and purple add to its allure.
- Chemical Composition: Calcium Aluminum Silicate Hydroxide.
- Hardness: 6.5 to 7 on the Mohs scale.
- Refractive Index: 1.691 – 1.700.
- Crystal System: Orthorhombic.
Because of its relative softness compared to sapphire or diamond (Mohs 7 and below), tanzanite is susceptible to scratching and chipping. It often lacks "toughness," meaning it can break if struck hard. Consequently, it is generally recommended for earrings or pendants rather than daily-wear rings.
History and Lore Tanzanite was introduced to the global market by Tiffany & Co. in 1968, following its discovery by a prospector named Manuel d’Souza in 1967. The marketing campaign by Tiffany hailed it as "the most beautiful blue gem to be discovered in 200 years." The Maasai people, indigenous to the region where tanzanite is found, attribute spiritual significance to the stone, believing it brings contentment and calmness. It is often associated with a unique birthday gift tradition: a father giving his child a tanzanite stone to mark the transition from childhood to adulthood.
Turquoise: The Ancient Talisman
Geological Formation and Sources Turquoise is an opaque, hydrous phosphate of copper and aluminum. Unlike tanzanite, which is a metamorphic gem, turquoise forms in the near-surface environment where acidic, copper-rich groundwater percolates through aluminum-bearing rocks (such as feldspar). Over millions of years, the precipitation of these minerals creates nodules and veins of turquoise. The color ranges from sky blue to greenish-blue, determined by the amount of copper (blue) or iron (green) present in the chemical formula.
Historically, turquoise has been mined for over,000 years. Notable sources include: * Iran (Persia): Historically the source of the finest "robin's egg blue" turquoise with a distinctive spiderweb matrix. * Southwestern United States: Nevada, New Mexico, and Arizona are home to significant deposits, particularly the famous "Lander Blue" and "Sleeping Beauty" mines. * China: Produces significant quantities of turquoise, often with a matrix pattern.
Gemological Properties Turquoise is valued for its unique color and matrix (the host rock remnants that create a web-like pattern on the surface).
- Chemical Composition: Hydrous Copper Aluminum Phosphate.
- Hardness: 5 to 6 on the Mohs scale (can be as low as 3).
- Refractive Index: 1.610 – 1.650.
- Specific Gravity: 2.60 – 2.90.
Due to its porosity and low hardness, turquoise is often stabilized (impregnated with a clear resin) to enhance durability and color retention. Unstabilized natural turquoise is rare and commands a premium among collectors.
History and Lore Turquoise is arguably the oldest birthstone on the December list. Ancient Egyptians adorned themselves with turquoise jewelry, and the Tutankhamun burial mask was heavily inlaid with the gem. In Persian culture, turquoise was worn as a protector against unnatural death, believed to shatter when its owner was in danger. Native American cultures, particularly the Navajo, Zuni, and Hopi, have integrated turquoise into their spiritual and artistic traditions for centuries, viewing it as a piece of the sky fallen to earth.
Zircon: The Diamond Impostor
Geological Formation and Sources Zircon is a mineral belonging to the group of nesosilicates. It is the oldest known mineral on Earth, with crystals found in Australia dating back 4.4 billion years. It forms in igneous and metamorphic rocks. While zircon comes in a variety of colors (red, brown, green, yellow), the blue zircon is the specific variety associated with December. It is important to distinguish zircon from cubic zirconia (CZ), a synthetic diamond simulant; natural zircon is a distinct, natural gemstone.
Major sources of gem-quality zircon include: * Cambodia: Known for producing high-quality blue and yellow zircon. * Sri Lanka: A traditional source for zircon of various colors. * Thailand: A major cutting and trading center for zircon. * Australia: Holds the oldest zircon crystals, though gem-quality material is less common.
Gemological Properties Zircon possesses a high refractive index (2.08), which gives it exceptional brilliance and fire, rivaling that of diamond. However, it is brittle and has poor toughness due to its crystal structure.
- Chemical Composition: Zirconium Silicate.
- Hardness: 6.5 to 7.5 on the Mohs scale.
- Refractive Index: 1.92 – 2.01.
- Specific Gravity: 4.6 – 4.7.
The blue color in zircon is typically achieved through heat treatment of brown zircon crystals, a process that is stable and widely accepted in the trade.
History and Lore The name "zircon" may derive from the Persian word zargun, meaning "gold-colored." Throughout history, zircon was believed to bring sleep, prosperity, and honor to its wearer. In the Middle Ages, it was thought to aid in spiritual awakening and help the wearer achieve wisdom. Its diamond-like appearance made it a popular gem in Victorian England, often set in jewelry as a less expensive alternative to diamonds.
Comparative Gemological Properties
To better understand the distinct characteristics of these three gems, the following table summarizes their key physical properties:
| Property | Tanzanite | Turquoise | Zircon (Blue) |
|---|---|---|---|
| Mineral Family | Zoisite (Group) | Phosphate | Nesosilicate |
| Chemical Formula | Ca₂Al₃(SiO₄)₃(OH) | Hydrous Copper Aluminum Phosphate | ZrSiO₄ |
| Hardness (Mohs) | 6.5 – 7 | 5 – 6 (can be lower) | 6.5 – 7.5 |
| Crystal System | Orthorhombic | Triclinic | Tetragonal |
| Refractive Index | 1.691 – 1.700 | 1.610 – 1.650 | 1.92 – 2.01 |
| Specific Gravity | 3.35 | 2.60 – 2.90 | 4.6 – 4.7 |
| Transparency | Transparent to Translucent | Opaque | Transparent |
Metaphysical Beliefs and Symbolism
While gemological science defines a stone by its physical properties, cultural traditions attribute specific metaphysical meanings to the December birthstones. These beliefs have been passed down through generations and remain a significant factor for many buyers.
- Tanzanite: Often referred to as the "stone of transformation," tanzanite is believed to facilitate a higher consciousness and spiritual awakening. It is associated with the throat and crown chakras, promoting clear communication and intuition.
- Turquoise: Known as the "master healer," turquoise is thought to align all chakras and anchor the wearer to the earth. It is widely regarded as a protective stone that absorbs negative energy and promotes emotional stability.
- Zircon: This stone is associated with honor, purity, and spiritual protection. It is believed to help with sleep and induce vivid dreams, as well as boost self-esteem and confidence.
Care and Maintenance
Given their varying hardness and toughness, the December birthstones require specific care to maintain their beauty.
Tanzanite Care Because of its brittleness and cleavage (a tendency to split along flat planes), tanzanite should be handled with care. It is best cleaned using warm water, mild soap, and a soft brush. Ultrasonic and steam cleaners should be strictly avoided as the vibrations and heat can cause fractures. It is advisable to store tanzanite jewelry separately in a soft cloth to prevent scratching by harder gems.
Turquoise Care Turquoise is a porous gem that is sensitive to chemicals, lotions, cosmetics, and even the natural oils of the skin. These substances can cause the stone to discolor or become dull over time. Cleaning should be done with a soft, dry cloth; avoid soaking the stone in water, especially if it has been stabilized or treated. Prolonged exposure to sunlight can also fade the color of some turquoise varieties.
Zircon Care Zircon is relatively hard but brittle. It can be damaged by sharp blows. Cleaning zircon is generally safe with warm soapy water and a soft brush. Ultrasonic cleaners are usually safe, but caution is advised if the stone has been fracture-filled (though this is rare for blue zircon). Extreme temperature changes should be avoided to prevent thermal shock, which can crack the stone.
Conclusion
The decision of which gemstone represents December is not a singular choice but a celebration of variety. Tanzanite offers a modern, rare, and vibrant violet-blue hue, representing the unique geological history of East Africa. Turquoise provides an ancient connection to the earth, a protective talisman worn by civilizations for millennia. Zircon brings unmatched brilliance and fire, a durable and sparkling alternative that rivals the diamond.
For the December-born individual, these three stones offer a spectrum of blue that reflects the cool clarity of winter. Whether chosen for their geological rarity, historical significance, or metaphysical properties, Tanzanite, Turquoise, and Zircon stand as the definitive and most cherished birthstones of the final month of the year.