December, the final month of the year, is represented not by a single birthstone but by three: turquoise, zircon, and tanzanite. Among these, perhaps the most captivating and unique is tanzanite, a gemstone so rare and visually arresting it has been likened to "a shard of sapphire from the skies." This relatively modern addition to the birthstone list has quickly captured the imagination of jewelers and collectors alike. As a December birthstone, tanzanite’s origins, gemological properties, and symbolic meaning make it not only a stunning adornment but also a gemstone of compelling cultural and geological significance.
This article delves deeply into the world of tanzanite, examining its history, formation, physical and optical characteristics, and the rich lore surrounding it. Whether you are considering purchasing a tanzanite jewelry piece, studying gemstones for academic purposes, or simply intrigued by the beauty and rarity of this December gem, this guide offers a comprehensive overview grounded in authoritative and verified sources.
History and Lore
Tanzanite may be a familiar name in modern jewelry, but its journey to the status of an official birthstone began in the 20th century. The gem was first discovered in the 1960s in the Merelani Hills near Arusha in Tanzania. The mineral originally identified was a type of zoisite, though it was the vibrant blue to violet hues that captured the attention of the mining community and the jewelry trade. What followed was a remarkable transformation. Tiffany & Co., the renowned American jewelry house, played a pivotal role in popularizing the gem. The company named the new jewel “tanzanite” after its country of origin and began distributing it to retailers in the early 1970s. The name, which quickly caught on in both industry and consumer circles, has now become synonymous with the beautiful blue zoisite.
The gemstone was officially recognized as a December birthstone in 2002 by the American Gem Trade Association (AGTA), in partnership with Jewelers of America. This addition marked the first change to the official U.S. birthstone chart in over 50 years. Prior to this, December was represented by blue topaz and turquoise.
The allure of tanzanite is partly due to its extremely limited geographic source. Unlike diamonds, sapphires, or many rubies that are found in multiple countries, tanzanite is found almost exclusively in Tanzania. This exclusivity has contributed to the gem's mystique and has made it one of the rarest birthstones in the world. Additionally, most tanzanite on the market today undergoes heat treatment to achieve and enhance the iconic blue to violet colors that define the stone.
While tanzanite does not have a long historical use like some of its counterparts—such as sapphire or ruby—its modern history is rich with symbolism and marketing. Promoted as a December birthstone that embodies "passion, love, and vitality," tanzanite quickly became a favorite among jewelry designers for its vibrant colors and unique optical traits.
Geological Formation and Sources
Understanding the geological origins of tanzanite is essential for appreciating its rarity and value. Tanzanite is a metamorphic gemstone, formed under specific and extreme pressure and heat conditions. It is a variety of the mineral zoisite, chemically known as Ca₂Al₃O₅(SiO₄)(OH)₃, and is distinguished from other zoisite varieties by the presence of vanadium. This vanadium is responsible for the stone’s signature blue and violet hues. The stone can also contain trace amounts of titanium and chromium, which further influence its coloration.
The Merelani Hills of northern Tanzania, located near the Kenyan border, are the sole natural source of tanzanite. The geology of the area includes a complex interplay of rock types, including alkali granite and metamorphic host rocks. Tanzanite forms in a very narrow zone, which is geologically unstable and subject to mining challenges. Its limited geographic origin means that tanzanite is one of the most geographically restricted gemstones available on the market today, and this scarcity plays a significant role in its commercial value.
Minerals in this family—such as thulite and clorite zoisite—can be found in locations like Norway and Brazil, but the blue-violet variety of zoisite known as tanzanite is exclusively found in Tanzania. As such, the stone is deeply tied to the land and cultural heritage of the area.
Mining tanzanite is both an industry and a livelihood for many in the region, though due to the fragile nature of the deposit, there are growing concerns about long-term sustainability. Some geological surveys suggest that the tanzanite deposits may be depleted within a few decades. This potential for scarcity has only heightened the stone’s value and allure in both the jewelry world and the broader gemological landscape.
The mining process for tanzanite is labor-intensive and dangerous. Artisanal miners, or in some cases small-scale commercial enterprises, extract the raw crystals from the earth and then cut and polished them into marketable gemstones. Some rough stones have been found in sizes as large as one kilogram, though most are smaller. The uncut crystals are often a vivid purple and require heat treatment to enhance their blue and violet hues fully.
Gemological Properties
To accurately identify, evaluate, and appreciate tanzanite, it is essential to understand its gemological properties. These characteristics help gemologists and buyers assess its quality and determine appropriate care and setting methods.
Color: Tanzanite is best known for its blue to violet color, often likened to a deep, vivid sapphire. This coloration is not natural in its raw form but is achieved through heat treatment, which is universally applied in the industry. The color shift typically occurs around 500–600°C. Some stones may also exhibit pleochroism, meaning they display different colors when viewed from different angles. For example, the same tanzanite might appear blue face up and violet from the side.
Clarity: Tanzanite is generally cut to enhance its color and to reduce the impact of inclusions or internal fractures. While inclusions are common in natural gemstones, tanzanite tends to have fewer visible inclusions compared to some other minerals in the zoisite family. However, it is still classified as a “type I” or “type II” gemstone for inclusions, which means small to moderate inclusions may be visible to the naked eye. These inclusions are considered part of the gem's natural beauty and character.
Hardness: Tanzanite has a Mohs hardness of 6 to 6.5, which is relatively soft compared to other gemstones such as sapphire (9) or zircon (6.5–7.5). This softness means that tanzanite is more prone to scratches and wear, especially if set in rings, which are subject to daily friction. A tabular display of common gemstone hardness provides helpful comparison context:
| Gemstone | Mohs Hardness |
|---|---|
| Diamond | 10 |
| Sapphire | 9 |
| Zircon | 6.5–7.5 |
| Tanzanite | 6–6.5 |
| Topaz | 8 |
| Turquoise | 5.5–6 |
Given tanzanite’s moderate hardness, it is best suited for earrings or pendants rather than rings where it may be subjected to more frequent damage. Proper setting and handling are essential for maintaining the gem’s appearance and integrity over time.
Cut: Tanzanite is commonly cut into facetted gemstones using various designs, including the antique cut, which is highlighted as a traditional cut in the industry. The faceting pattern is chosen not only for beauty but also to optimize the gemstone’s refractive qualities and color enhancement.
Refractive Index and Luster: Tanzanite has a refractive index of approximately 1.69 to 1.71, which is slightly higher than that of quartz but lower than sapphire or zircon. It features a glassy to subadamantine luster, giving it a brilliant, polished appearance. Tanzanite also displays a double refraction effect, which means light entering the gem splits into two rays, potentially creating a visible doubling of facets when viewed through a loupe.
The chemical properties of tanzanite, like those of all minerals, influence its color stability and environmental sensitivity. The stone is susceptible to high heat or prolonged exposure to sunlight, which may cause the treated blue color to fade or shift to an over-saturated or brownish hue. UV light and certain chemicals can also impact the gem, so care should be taken to store and clean it appropriately.
Symbolism and Metaphysical Beliefs
While tanzanite may be one of the younger additions to the birthstone list, it has quickly acquired its own set of symbolic and metaphysical meanings. Modern sources classify tanzanite as a gemstone of clarity, transformation, and spiritual insight.
In metaphysical traditions, tanzanite is said to open the third eye and throat chakras, enhancing one’s ability to see beyond the material world and to express one’s inner truth. It is believed to encourage emotional healing, helping individuals process grief, trauma, and the subconscious. Some practitioners also associate tanzanite with interdimensional travel, meditation, and dream work, suggesting it is a stone that bridges physical and spiritual realms.
The color of tanzanite, particularly its rich blue and violet tones, is often linked with emotional balance, calm, and inner peace. Historically, blue has been associated with wisdom, stability, and communication, all of which are strengthened by tanzanite. Violet, on the other hand, relates to the crown chakra, symbolizing spiritual connection and enlightenment.
It is important to note, however, that most of these beliefs are based on modern metaphysical traditions rather than historical or traditional lore. Unlike older birthstones such as sapphire or emerald, which are backed by extensive classical literature and historical use, tanzanite's symbolic meaning is primarily derived from contemporary new age practices. That said, its modern popularity and accessibility have allowed it to become a significant gemstone in the world of spiritual and alternative healing.
In terms of traditional symbolism, much of what applies to tanzanite is borrowed from other December birthstones like turquoise and zircon. The idea of tanzanite as a stone of protection, healing, and truth-telling aligns closely with the broader themes associated with December-born gems, even without a deep historical lineage.
Care and Cleaning
Given tanzanite's relatively low hardness and sensitivity to environmental factors, proper care and cleaning are essential to preserving its beauty and longevity.
Cleaning Method: Tanzanite can be cleansed using soapy water with a soft brush to gently remove surface dirt and oils. It should not be exposed to harsh chemicals such as bleach, ammonia, or acidic cleaners, which can damage the gem's surface or affect the stability of its color. Ultrasonic and steam cleaners are also discouraged, as they can cause the stone to crack or fade due to its internal fractures and heat-sensitive properties.
Storage: Tanzanite should be stored separately from harder gemstones to prevent scratches. A soft cloth or a fabric-lined jewelry box is ideal, keeping it covered to avoid prolonged exposure to light and heat.
Handling: Tanzanite is most appropriately used in low-wear settings such as pendants or earrings. For rings, it should ideally be set in a protected mounting to avoid direct contact with abrasive surfaces.
Repairs and Setting: When repairing or setting a tanzanite piece, jewelers should be aware of the stone’s modest hardness and tendency to fracture under stress. It is important to avoid any tools or techniques involving high heat or excessive mechanical force.
Conclusion
Tanzanite represents the modern evolution of the birthstone concept—a gem not only of exceptional beauty but also of symbolic richness and geological rarity. Discovered in 1960s Tanzania and popularized by Tiffany & Co., tanzanite was officially designated as a December birthstone in 2002, marking the first addition in over half a century to the standard U.S. list.
From a gemological standpoint, tanzanite is a unique member of the zoisite mineral family known for its striking blue to violet colors (after heat treatment), moderate hardness, and appealing refractive qualities. While not found in ancient texts, it has quickly become associated with themes of emotional healing, spiritual insight, and clarity, particularly in modern metaphysical circles.
In jewelry, tanzanite stands out not only for its vibrant hues but for its limited geographic source, which adds to its allure and exclusivity. As the potential for tanzanite to become one of the rarest and hardest-to-source gemstones increases, its value and demand among collectors and jewelry enthusiasts are expected to rise.
For those born in December, tanzanite offers a beautiful and meaningful birthstone that reflects both the year’s end and the promise of what is to come. Whether valued for its aesthetic appeal, rare origin, or healing properties, tanzanite continues to capture the imagination of the modern gemstone world.