Tourmaline stands as a testament to nature’s artistic versatility, holding the distinguished position as one of the two official birthstones for October. Renowned for its unparalleled spectrum of colors, this gemstone derives its name from the Sinhalese words “tura mali,” meaning “mixed stones,” a moniker that accurately reflects its diverse appearance. Unlike many other gem species that are defined by a single hue, tourmaline encompasses a vast array of varieties, from the deep blacks of schorl to the vivid electric blues of paraiba. This diversity is not merely aesthetic; it is rooted in the gem’s complex mineralogy and geological formation.
For gemstone enthusiasts, jewelry buyers, and students of gemology, tourmaline offers a fascinating study in complexity. It is not a single mineral but a group of complex borosilicates with varying chemical compositions. This variability allows for a wide range of physical properties and colors, making it a favorite among lapidaries and collectors. The following sections will explore the rich history of tourmaline, its geological origins, its precise gemological characteristics, and the metaphysical beliefs that have surrounded it for centuries.
History and Lore
The history of tourmaline is as colorful as the gem itself. While it has been appreciated for centuries, its formal recognition in the gem trade is a relatively recent development. The name "tourmaline" originates from the Sinhalese term "tourmali," which early gem traders used to describe the mixed stones found in the gravel of regions such as Sri Lanka and Burma. Because early traders relied primarily on color to identify gems, tourmaline was often confused with other stones. Red tourmaline was frequently mistaken for ruby, while blue varieties were sold as sapphire. It was not until the development of modern optical gem testing equipment that gemologists were able to distinguish tourmaline from these other corundum varieties and properly identify its unique gemological properties.
The first recorded discovery of green tourmaline occurred in 1554, when Francisco Spinoza’s expedition in Brazil discovered crystals that were initially called "Brazilian emerald." This marked the beginning of tourmaline's journey into the broader gem market. However, despite its long history, tourmaline did not immediately gain status as a traditional birthstone. For many years, opal was the sole birthstone for October.
The inclusion of tourmaline as an October birthstone is a modern adaptation. In 1952, the Jewelry Industry Council suggested that pink tourmaline be added as an alternate stone to opal. This proposal was accepted and approved by the American Gem Society and the National Retail Jewelers Council. Although the original designation specified pink tourmaline, the practice has evolved to accept tourmaline of any color as a valid birthstone for October, reflecting the gem’s incredible variety. Beyond its association with birthdays, tourmaline also serves as the symbolic gem for couples celebrating their eighth wedding anniversary.
Geological Formation and Sources
Tourmaline is a complex silicate of boron and aluminum, belonging to a mineral supergroup that comprises multiple groups, subgroups, and over thirty distinct species. The gem’s formation requires specific geological conditions, typically found in metamorphic and igneous rocks. The complex chemistry of tourmaline allows for the substitution of various elements, which directly influences its color.
One of the most significant sources of tourmaline, particularly the green varieties, is Brazil. The country is also home to the famous Paraiba tourmaline, a variety colored by copper that displays vivid blue to green hues. The discovery of these copper-bearing tourmalines in the Paraiba state of Brazil revolutionized the market, introducing colors previously unseen in the gemstone world.
Beyond Brazil, tourmaline is found in various other localities. Sri Lanka and Burma are historically significant for producing tourmaline in gravel deposits, where the gem shares the alluvial environment with other stones like ruby, sapphire, peridot, and spinel. The United States, specifically Maine and California, has also been a notable producer of tourmaline. The gemstone's global distribution ensures a steady supply, though the finest specimens—particularly those with intense, saturated colors—command premium prices in the market.
Gemological Properties
The physical and optical properties of tourmaline are key to its identification and valuation. As a group, tourmaline displays a range of characteristics that are consistent enough for identification but varied enough to require careful analysis.
Color and Pleochroism Tourmaline is perhaps best known for its "all colors" palette. The gem’s color is determined by trace elements within its crystal structure. Iron and titanium are generally responsible for green and blue colors, while manganese produces reds and pinks. Some pink and yellow tourmalines may owe their hues to color centers caused by radiation. Tourmaline exhibits strong pleochroism, meaning it displays different colors when viewed from different crystal directions. This property is evident in transparent crystals when viewed perpendicular to the c-axis versus parallel to it.
Crystal Habit and Structure Tourmaline crystallizes in the trigonal system and is characterized by long, prismatic crystals that often have a distinctive triangular cross-section. The outer surfaces of these crystals are usually deeply striated, running parallel to the length of the crystal. This elongated habit influences how the stone is cut; lapidaries must orient the stone so that the table is parallel to the c-axis. If the table is perpendicular to the c-axis, the stone can develop a very dark body color due to light absorption along that axis.
Hardness and Durability With a Mohs hardness of 7 to 7.5, tourmaline is considered a durable gemstone suitable for all types of jewelry, including rings and bracelets that are subject to daily wear. Its hardness provides good resistance to scratching, though care should still be taken to avoid contact with harder materials like diamond or corundum.
Refractive Index and Optical Characteristics Tourmaline has a refractive index ranging from 1.624 to 1.644 and a birefringence of 0.018 to 0.040. These values allow for some doubling of back facets and inclusions when viewed through the table. The gem typically exhibits a soft luster. Additionally, tourmaline is known for its pyroelectric and piezoelectric properties; it becomes electrically charged when heated or squeezed.
Specific Gravity The specific gravity of tourmaline ranges from 3.06 (+0.20, -0.06), which is a useful metric for distinguishing it from other gemstones of similar appearance.
Summary of Key Gemological Properties
The following table summarizes the essential gemological data for tourmaline, based on standard references:
| Property | Value / Description |
|---|---|
| Chemistry | Complex Borosilicate (e.g., Elbaite: Na(Li1.5,Al1.5)Al6Si6O18(BO3)3(OH)4) |
| Crystal System | Trigonal |
| Mohs Hardness | 7 to 7.5 |
| Refractive Index | 1.624 to 1.644 |
| Birefringence | 0.018 to 0.040 |
| Specific Gravity | 3.06 (+0.20, -0.06) |
| Colors | All colors |
Varieties and Phenomena
The diversity of tourmaline gives rise to several distinct varieties and optical phenomena that are highly prized by collectors.
Watermelon Tourmaline One of the most iconic varieties is watermelon tourmaline. This variety features a crystal structure where the outer layer is green and the interior is red or pink. The visual effect mimics the appearance of a watermelon slice. The distinction is now used for any tourmaline that displays an outer layer of one color and an interior of another, though the classic green-pink combination remains the most sought after.
Particolor Tourmaline Particolor tourmaline refers to stones that display two or more distinct colors within a single crystal or cut stone. This can occur naturally due to zoning within the crystal or as a result of cutting the stone to highlight contrasting color zones.
Black Tourmaline (Schorl) Black tourmaline, known as schorl, is rich in iron and ranges from deep browns to bluish-blacks. While often used for industrial purposes, schorl is also popular in metaphysical circles for its grounding and protective properties.
Dravite Dravite is the brown variety of tourmaline, characterized by its magnesium-rich composition. It displays warm, earthy tones ranging from deep browns to vibrant yellows.
Paraiba Tourmaline The Paraiba variety, colored by copper, is famous for its intense blue to green hues. These stones are among the most valuable tourmalines due to their rarity and vivid saturation.
Symbolism and Metaphysical Beliefs
Throughout history, tourmaline has been attributed with various symbolic meanings and metaphysical powers. While these beliefs are not scientifically verified, they form an integral part of the gem's cultural legacy.
The gem's name, meaning "mixed stones," suggests a connection to balance and harmony. In modern metaphysical beliefs, different colors of tourmaline are associated with different chakras or energies. Black tourmaline (schorl) is widely regarded as a protective stone, believed to ward off negative energies and provide grounding. It is often used in spiritual practices to cleanse one's aura.
The vibrant colors of tourmaline, particularly the pinks and reds, are often associated with love, vitality, and emotional healing. As a birthstone for October, it symbolizes love, luck, and personal empowerment. The watermelon variety, with its distinct layers, is specifically linked to the heart chakra and is believed to promote kindness, compassion, and emotional balance.
In the context of anniversaries, tourmaline serves as a token for the eighth year of marriage, representing the deepening and diversification of a relationship, much like the gem's own spectrum of colors.
Care and Cleaning
Given its excellent durability, tourmaline is relatively easy to care for, making it an ideal gemstone for everyday jewelry. However, specific guidelines should be followed to maintain its beauty.
Hardness and Cleavage With a hardness of 7 to 7.5, tourmaline resists scratching better than many other gemstones. However, it does possess perfect cleavage in one direction, meaning it can split along specific planes if struck with sufficient force. This makes it susceptible to damage from sharp impacts. Therefore, tourmaline jewelry should be stored separately from other pieces to avoid scratching and protected from hard knocks.
Cleaning Methods Tourmaline can be safely cleaned using warm water, mild soap, and a soft brush. Ultrasonic cleaners are generally safe for tourmaline, provided the stone does not have any significant fractures or inclusions that could be exacerbated by vibrations. Steam cleaning is also acceptable for untreated and fracture-filled stones, but caution is advised for stones that have undergone heat treatments or fillings.
Heat Sensitivity Tourmaline can be sensitive to sudden temperature changes. Extreme heat can cause existing fractures to widen or alter the stone's color. Therefore, it is advisable to avoid exposing tourmaline jewelry to rapid temperature fluctuations, such as moving from a hot tub to cold air.
Storage When storing tourmaline, keep it in a soft cloth or a separate compartment in a jewelry box. This prevents the gem from coming into contact with harder stones like diamonds or corundum, which could scratch its surface.
Conclusion
Tourmaline is a gemstone of remarkable complexity and beauty. Its status as an October birthstone is well-deserved, reflecting not only its visual appeal but also its rich history and geological diversity. From the ancient confusion with rubies and sapphires to the modern discovery of the vivid Paraiba varieties, tourmaline has continually captivated the gem world.
Its unique trigonal crystal structure, coupled with a hardness of 7 to 7.5, makes it a durable choice for jewelry, while its vast color range ensures that there is a tourmaline to suit every taste. Whether valued for its metaphysical properties, its symbolic significance as an eighth-anniversary gift, or simply its aesthetic brilliance, tourmaline remains a cornerstone of the gemstone market. For those born in October, or for anyone who appreciates the artistry of nature, tourmaline offers a tangible connection to the earth's hidden wonders—a medley of colors and energies that continues to inspire and endure.