The world of birthstones is a fascinating intersection of geology, history, and cultural symbolism. Each month is associated with specific gemstones that offer a unique palette of color and meaning. December, in particular, stands out with a diverse array of blue gemstones, while March is elegantly represented by a single, serene stone. This article provides a detailed examination of the gemstones associated with these months, focusing on their geological origins, gemological properties, historical significance, and practical care. The primary focus will be on the four modern birthstones for December—blue zircon, blue topaz, tanzanite, and turquoise—and the singular traditional and modern birthstone for March, aquamarine.
History and Lore
The tradition of assigning specific gemstones to months has evolved over centuries. The modern list, largely standardized in the early 20th century, often includes stones that were popular in historical jewelry. For March, aquamarine has long been associated with the month. Its name derives from the Latin aqua marina, meaning "sea water," a fitting description for its characteristic blue-green hues. Historically, aquamarine was believed to be a treasure of mermaids and was used by sailors as a talisman for safe passage across treacherous seas. It was also thought to possess healing properties and to promote clarity and calmness.
December's birthstones have a more complex history, with several stones sharing the honor. The traditional December stones are turquoise and lapis lazuli, while the modern additions are blue zircon, blue topaz, and tanzanite. Turquoise is one of the oldest gemstones known to humanity, with a history spanning over 2000 years. It was extensively used by ancient civilizations in Egypt, Persia, and the Americas. In the Southwestern United States, Native American cultures have a profound connection to turquoise, creating intricate jewelry, beads, and inlay work. The stone is traditionally associated with protection, good fortune, and spiritual grounding.
Zircon, another traditional December stone, has been used for centuries. It is often confused with cubic zirconia, a synthetic diamond simulant, but natural zircon is a distinct and valuable gem. Historically, zircon was believed to promote wisdom, honor, and purity. It was also thought to help with sleep and ward off evil spirits.
Tanzanite is a relative newcomer to the gemstone world. Discovered in Tanzania in the 1960s, it was added to the modern birthstone list in 2002. Its rapid rise to prominence is due to its unique violet-blue color and its limited geographic source. Symbolically, tanzanite is linked to transformation, new beginnings, and spiritual awakening.
Blue topaz was added to the December birthstone list later than the others, around 1952. While topaz occurs in a wide range of colors, the blue variety became particularly popular for its crisp, wintry blue hue. The discovery of large deposits in Brazil in the latter half of the 20th century made blue topaz more accessible and affordable, solidifying its place as a modern December birthstone.
Geological Formation and Sources
The gemstones for December and March originate from different geological environments, which influences their properties and availability.
March: Aquamarine
Aquamarine is a variety of the mineral beryl, which also includes emerald and morganite. It forms in pegmatites—coarse-grained igneous rocks that develop from the slow cooling of magma. During this process, beryllium, aluminum, silicon, and oxygen combine to form beryl, with trace elements like iron impuritying the crystal lattice to produce the blue-green color. Major sources for aquamarine include Brazil, Nigeria, Madagascar, and Pakistan.
December: A Trio of Blue Gems
The four December birthstones each have distinct geological origins:
Turquoise: This is a hydrated phosphate of copper and aluminum. It forms in arid regions where acidic, copper-rich groundwater percolates through rocks containing aluminum and phosphorus. Over millennia, this process creates turquoise nodules in host rock. Notable sources include the United States (Arizona, New Mexico, Nevada), Iran, China, and Mexico. The stone is often found in a matrix, a web-like pattern of host rock (such as chert or limonite) that can affect its color and durability.
Zircon: Zircon is a zirconium silicate (ZrSiO₄) that forms in igneous and metamorphic rocks. It is one of the oldest minerals on Earth, with some crystals dating back billions of years. While zircon is found worldwide, significant gem-quality deposits come from Cambodia, Sri Lanka, and Australia. The blue variety is typically produced by heat-treating brown zircon, a common practice in the gem trade.
Tanzanite: This unique gemstone is a variety of the mineral zoisite. It is found in only one location on Earth: the Merelani Hills of northern Tanzania, near Mount Kilimanjaro. Its formation is linked to a specific geological event—the metamorphism of calcareous rocks by heat and pressure from igneous intrusions. This unique process, combined with the presence of vanadium for its color, makes tanzanite exceptionally rare.
Blue Topaz: Topaz is a silicate mineral containing fluorine and aluminum. It forms in pegmatites and high-temperature veins. While topaz occurs in many colors, the natural blue variety is rare. Most of the blue topaz in the market is the result of irradiating and heat-treating colorless or pale yellow topaz, a stable and industry-accepted process. Major sources include Brazil, the United States, Sri Lanka, and Nigeria.
Gemological Properties
Understanding the physical and chemical properties of these gemstones is crucial for jewelers, collectors, and anyone interested in their care and valuation.
Aquamarine (March)
As a member of the beryl family, aquamarine shares properties with emerald but is generally more included-free. Its hardness on the Mohs scale is 7.5 to 8, making it durable enough for everyday jewelry. Its refractive index ranges from 1.577 to 1.583, and it has a vitreous luster. The most prized color is a clear, medium to deep blue, with a slight greenish hue being acceptable. Unlike emerald, aquamarine is not typically treated for clarity, though some stones may be heat-treated to enhance their blue color.
December Gemstones
The four December stones vary significantly in their gemological characteristics:
| Gemstone | Mineral Family | Chemical Composition | Mohs Hardness | Refractive Index | Common Treatments | Notable Properties |
|---|---|---|---|---|---|---|
| Aquamarine | Beryl | Be₃Al₂(SiO₃)₆ | 7.5 - 8 | 1.577 - 1.583 | Heat treatment for color | Vitreous luster, good clarity |
| Turquoise | Phosphate | CuAl₆(PO₄)₄(OH)₈·4H₂O | 5 - 6 | 1.610 - 1.650 | Stabilization, dyeing | Opaque, often matrix-included |
| Zircon | Zirconium Silicate | ZrSiO₄ | 6.5 - 7.5 | 1.925 - 1.984 | Heat treatment for color | High refractive index, high dispersion |
| Tanzanite | Zoisite | Ca₂Al₃(SiO₄)₃(OH) | 6.5 - 7 | 1.691 - 1.700 | Heat treatment (standard) | Strong trichroism (blue, violet, burgundy) |
| Blue Topaz | Silicate | Al₂(F,OH)₂SiO₄ | 8 | 1.609 - 1.617 | Irradiation & heat treatment | Good durability, large sizes available |
Turquoise is the softest and most porous of the group (Mohs 5-6). It is almost always opaque and is commonly cut into cabochons. Most commercial turquoise is treated—either stabilized with resin to improve hardness and color, or dyed to enhance uniformity.
Zircon is notable for its high refractive index and strong dispersion ("fire"), which can rival diamond. However, it is more brittle due to its perfect cleavage in two directions. Most blue zircon is heat-treated from brownish crystals.
Tanzanite is prized for its strong trichroism—the ability to show three different colors (typically blue, violet, and burgundy) when viewed from different crystal directions. It is standard practice to heat tanzanite to about 500-600°C to remove the brownish component and develop its signature blue-violet color. With a hardness of 6.5 to 7, it requires careful handling to avoid chipping.
Blue Topaz is the hardest and most durable of the December stones (Mohs 8), making it an excellent choice for rings and daily-wear jewelry. The blue color in most commercial topaz is the result of irradiation followed by heat treatment, a process that creates a stable, permanent color. Natural blue topaz is exceedingly rare.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, these gemstones are steeped in symbolism and metaphysical lore.
Aquamarine: Associated with the throat chakra, aquamarine is believed to facilitate clear communication, courage, and emotional balance. It is often called the "stone of courage" and is thought to soothe fears and reduce stress.
Turquoise: A stone of protection, turquoise is believed to ward off negative energy and bring good fortune. It is associated with the sky and water, symbolizing peace, tranquility, and spiritual grounding. In many cultures, it is considered a sacred stone that connects the wearer to the natural world.
Zircon: Known as a stone of wisdom and clarity, zircon is believed to help with focus, mental clarity, and spiritual growth. It is also associated with honor and purity. Some traditions hold that zircon can aid in sleep and promote prosperity.
Tanzanite: As a stone of transformation, tanzanite is linked to new beginnings, spiritual awakening, and higher consciousness. Its unique color is said to bridge the gap between the physical and spiritual realms, encouraging mindfulness and intuition.
Blue Topaz: Blue topaz is associated with calm, clarity, and communication. It is believed to promote truth, wisdom, and self-realization. Its cool blue color is thought to evoke feelings of peace and serenity, making it a popular stone for meditation and stress relief.
Care and Cleaning
Proper care is essential to maintain the beauty and integrity of these gemstones, given their varying levels of hardness and stability.
Aquamarine: With a hardness of 7.5-8, aquamarine is relatively durable. It can be cleaned with warm, soapy water and a soft brush. Ultrasonic cleaners are generally safe, but steam cleaning should be avoided due to potential fractures from heat or impact.
Turquoise: Due to its softness (Mohs 5-6) and porosity, turquoise requires gentle care. It should be cleaned with a soft, dry cloth. Avoid chemicals, including household cleaners, cosmetics, and perfumes, which can damage the stone. Prolonged exposure to water, heat, or sunlight can cause fading or cracking. It is not suitable for ultrasonic or steam cleaning.
Zircon: While hard, zircon has perfect cleavage, making it susceptible to chipping from sharp blows. It should be protected from hard knocks. Clean with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and sudden temperature changes, which can cause internal stress.
Tanzanite: With a hardness of 6.5-7 and cleavage, tanzanite is more fragile than aquamarine or topaz. It is best suited for pendants or earrings rather than rings. Clean gently with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam, as vibrations and heat can cause damage. Store separately to prevent scratching.
Blue Topaz: As the hardest of the group (Mohs 8), blue topaz is quite durable and suitable for all jewelry types. It can be cleaned with warm, soapy water and a soft brush. Ultrasonic cleaners are typically safe, but steam cleaning should be approached with caution if the stone has inclusions or fractures.
Conclusion
The birthstones of December and March offer a remarkable study in diversity, from the ancient, earthy turquoise to the modern, transformative tanzanite. March is beautifully represented by aquamarine, a durable and serene gem with a deep connection to the sea. December provides a rich palette of blue stones, each with its own geological story, cultural significance, and practical considerations. Whether chosen for their historical lore, symbolic meaning, or simply their captivating color, these gemstones continue to enchant and inspire. Understanding their properties and origins allows for a deeper appreciation of these natural treasures and ensures they can be enjoyed for generations to come.