Tourmaline is a name applied to a family of related minerals with widely varying properties. Tourmalines make very popular jewelry stones and come in an amazing range of colors, including multi-color zones. Pink tourmaline – the modern October birthstone – is a particularly popular color.
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Ready availability keeps tourmaline prices reasonable. Small tourmalines (under 5 carats) are fairly easy to obtain at modest cost. Only when you get into large sizes or extremely rare or fine colors do prices go over a few hundred dollars per carat.
Most colors are fairly common, but pure blue, red, orange, yellow, and purple stones are rare. Such stones usually command higher prices. Color-change tourmalines are also exceptionally rare. Neon-blue paraíba tourmalines, raspberry-red rubellites, and emerald-green chrome tourmalines are especially prized.
Tourmaline crystals are often cracked and flawed, which puts a premium on clean gemstones, especially those over 10 carats in weight. Generally, the only acceptable types of inclusions in cut tourmalines are the tubes that, when densely packed, produce a cat’s eye effect in cabochons. The “eye” in a cat’s eye tourmaline can be very strong, especially when set against a richly colored gem.
Varies by species, 0.006–0.080, but usually around 0.020. Also note that the absorption of the O ray is sometimes strong enough to plane polarize light. At times it is totally absorbed and will show a single line in a refractometer.
Tourmalines are usually weak to inert in UV light. Pink stones: inert to very weak red to violet. Other colors, generally inert. Stones may be chalky blue to strong blue in SW (Newry, Maine). Pink gems from Brazil may be blue or lavender in SW, and gems from Tanzania (golden yellow, brown, and green stones) are strong yellow in SW.
Tourmaline is from the Singhalese word turamali, meaning “mixed-colored stones.”Tourmalines were often confused with other gems. Dravite is named after the Carinthian district of Drave, Austria. Schorl is an old German mining term for unwanted minerals associated with ore. Elbaite is named after the Isle of Elba, Italy. Buergerite is named after Professor Martin J. Buerger, crystallographer and well-known research scientist. Liddicoatite is named after Richard T. Liddicoat, the former director of the Gemological Institute of America. Chromdravite is named for its composition. Uvite is named after the Uva Province, Sri Lanka.
Tourmaline occurs in crystalline schists; in granites and granite pegmatites (especially elbaite); in gneiss, marbles, and other contact metamorphic rocks (especially dravite, uvite). Tourmaline is also found as inclusions in quartz.
Tourmaline is a mineral supergroup that consists of three groups, multiple subgroups, and over thirty different species. With new discoveries, the list of tourmaline species continues to grow. They all have the same trigonal (hexagonal) crystal structure but different chemical formulas.
The Victorian writer John Ruskin’s quip from 1890 still applies to tourmalines today:
The chemistry of [tourmaline] is more like a medieval doctor‘s prescription than the making of a respectable mineral.
X, Y, Z, T, V, and W can represent different elements, so many substitutions and, hence, variations are possible. This chemical complexity can create a vast array of appealing colors in tourmalines, including multi-color patterns.
In addition, tourmaline crystals occur in abundance worldwide, often cuttable and sometimes large and well-terminated. These factors keep tourmalines priced low in general and highly popular with consumers.
All members of the tourmaline supergroup are considered tourmalines. The properties of some species are so close that separating them proves difficult. For gemological purposes, it’s sufficient to identify them all as tourmaline.
Tourmalines are piezoelectric as well as pyroelectric. They generate electricity when placed under pressure and heated, respectively. They also generate an electrostatic charge when rubbed.
Tourmalines come in all colors, from colorless to black. Crystals are frequently color zoned along their length (bi-color, tri-color, parti-color, and so forth) or concentrically zoned (watermelon tourmaline).
The vast majority of cut tourmaline gemstones belong to the elbaite species. Other species you might find cut or in jewelry are dravite, liddicoatite, schorl, and uvite. You’ll rarely encounter other tourmaline species cut as gemstones, but they do show up occasionally.
The following table breaks down the difference in optical and physical properties between various species. (Note that all tourmalines have the same optic character and dispersion. Hardness can vary from 7 to 7.5). The species most commonly encountered as gemstones are listed in bold italic type.
Variations in Properties by Tourmaline Species
Although you might find specimens described as buergerite, the correct name for this tourmaline species is fluor-buergerite. The “W” site in its chemical formula is fluorine (F). (“Buergerite,” with oxygen-hydrogen (OH) in the “W” site, has not been found).
These rare, dark brown to black crystals may have a bronze-colored iridescence under the surface.
Although the name refers to tourmalines with complex, multi-colored zoning, these stones may belong to two species. For years, scientists believed liddicoatite was a type of elbaite. In 1977, it was determined to be a calcium analogue to elbaite (with Ca in the “X” site). Years later, liddicoatite was redefined. Fluor-liddicoatite is F-dominant (“W” site), while liddicoatite is OH-dominant (“W” site). Investigations to determine if OH-dominant liddicoatite exists in nature continue. For now, it’s not an approved species name. However, the term “liddicoatite” is still popularly used to refer to stones that are actually fluor-liddicoatites.
Magnesium-dominant (Mg in the “Y” site) foitite with greenish brown to bluish gray color.
Tourmaline with colors ranging from blue to pale shades of pink, blue, or green, as well as colorless.
In 1997, researchers determined this rare tourmaline, formerly known as ferridravite, was not actually the ferric (Fe3+) analogue of dravite. It has a nearly opaque, dark brown, brownish black, or black color.
A rare, pink to tan tourmaline.
Black schorl has been used in jewelry since ancient times. During the Victorian Era, schorl frequently appeared in mourning jewelry. In modern times, this common tourmaline is seldom cut into gemstones. Schorl also occurs in brown, blue, or blue-green shades.
Tsilaisite was first proposed as a name for a hypothesized manganese-dominant (Mn) tourmaline species in 1929. In the mid-1980s, discoveries in Zambia of yellow tourmalines with high Mn content prompted some researchers to assert these were natural tsilaisites. Vendors even began using this name, despite it being unapproved and the stones falling short of the criteria for a new species. In 2006, researchers determined these stones were only Mn-rich elbaites and discredited the name. When tested in 2011, more than 200 candidate stones from all over the world failed to have the Mn content (>10.71 wt.% MnO) required for classification as tsilaisites.
However, in 2012, yellow tourmalines discovered in Elba, Italy proved to be the elusive Mn-dominant species (with Mn in the “Y” site). Thus, the tsilaisite species was finally officially approved.
Another revised and re-approved species (in 2020), uvites form a tourmaline subgroup, consisting of uvite proper, fluor-uvite, and feruvite. Most uvite specimens are actually fluor-uvite, the common, F-dominant member (with F in the “W” site).
Uvites have a wide range of colors: black, light to dark green, brown, red, and occasionally other colors, including colorless.
A vanadium-bearing dravite with dark green to black color.
There are many trade names for tourmalines, based on their color and appearance. Though their characteristics may coincide with those of specific species, the following are not species names. For example, rubellites are typically elbaites but may also be liddicoatites and olenites. Paraíba tourmalines were long thought to be exclusively elbaites, until copper-bearing liddicoatites with paraíba colors were identified in 2017.
Although an official species, the dravite name is sometimes applied to yellow and brown tourmalines, even if they don’t belong to that species.
Intense, neon-blue tourmalines colored by copper. Originally discovered in and named after the Brazilian state of Paraíba, specimens have also been found in Nigeria and Mozambique. The gem community largely accepts the definition of paraíba tourmalines by color and copper content. However, you might find some dealers reserve the term for the Brazilian material, referring to the African material as “paraíba-like” or just cuprian blue tourmaline.
Tourmalines with blue colors not caused by copper are called indicolites.
Tourmalines that have more than one color.
The term rubellite typically refers to tourmaline with reasonably saturated dark pink to red colors and medium to dark tones, from raspberry to ruby-like red. These stones are often strongly purplish, orangish, or brownish.
When sliced perpendicular to the c axis, trapiche tourmalines show inclusions formed from organic matter between growth sectors of its crystal structure, which resemble spokes radiating from the center of a wheel. Though these patterns may appear star-like, these aren’t star stones.
Green tourmalines. Stones with deep green color caused by chromium or vanadium are considered chrome tourmalines.
Although tourmalines are popular gems, other gem names may have more caché and command higher prices. As a result, some unscrupulous vendors might use evocative but deceptive combinations of gem names to sell tourmalines more easily. For example, you might encounter green tourmalines sold as “Brazilian emeralds” or “Ceylonese peridots” and blue tourmalines sold as “Brazilian sapphires.”
These terms are not acceptable trade names for tourmalines. Of course, tourmalines, emeralds, peridots, and sapphires are all distinct gem species. Emeralds and sapphires are also quite a bit more expensive than most tourmalines. To complicate matters, emeralds really do occur in Brazil, and peridots do occur in Sri Lanka. Ask vendors to clarify the names and sources of any tourmalines they sell or ask for a gem lab analysis, especially for any high-value gemstones.
The absorption of the o-ray in tourmaline is strong enough to plane-polarize light. Sometimes, this ray is totally absorbed and a tourmaline may appearisotropic, because it shows only one absorption edge on the refractometer.
Dark green and brown tourmalines display especially strong pleochroism, while pale colors have weak dichroism. Light traveling along the length of a prismatic crystal always shows a deeper color than at right angles to this direction.
Most tourmalines fall under the Type II clarity category, “Usually Included.” Green tourmalines are Type I, “Usually Eye Clean,” while red and watermelon tourmalines are Type III, “Almost Always Included.”
All tourmalines may contain inclusions of hollow tubes, elongated or irregular thread-like cavities, sometimes with liquid or gas inclusions, sometimes two-phase inclusions, often in mesh-like patterns. The tubes usually run parallel to the length of crystals and, when densely packed, may produce a chatoyant effect in cabochons.
Red tourmalines may contain gas-filled fractures as well as flat films that reflect light and appear black.
Tourmalines may contain mineral inclusions of hornblende, mica crystals, apatite, and zircon.
Some clear quartz stones may contain needle-like inclusions of black tourmaline crystals. Referred to as tourmalinated quartz, these pieces can make attractive display crystals as well as intriguing gemstones for jewelry.
Scientists have produced synthetic tourmalines for research purposes. For example, before the discovery of tsilaisite in nature, researchers had produced it the laboratory (1984) as well as other Mn-rich tourmalines (2003).
However, is there any lab-created tourmaline commercially available for gem or jewelry use?
In 1993, Russian scientists synthesized tourmalines via a hydrothermal process. In this case, synthetic tourmaline was grown over natural tourmaline seed crystals. Curiously, in 2008, the International School of Gemology (ISG) — not the International Gem Society (IGS) — concluded that some unusual tourmalines it acquired were most likely synthetics manufactured like those in the 1993 experiment. As the news of that declaration spread, so did rumors that these synthetics had entered the gem market.
Bear Williams of Stone Group Labs debunked that rumor. In his 2009 article, he wrote that the 1993 experiment only produced a minuscule amount of synthetic tourmaline at great cost. Furthermore, he noted that the ISG had made errors comparing the Raman spectroscopy of its specimens to those examined during the 1993 research. (In a response, the ISG reported that it reevaluated its tourmaline specimens and determined they were actually natural liddicoatites, not synthetics).
Synthetic tourmaline is expensive and difficult to create. Furthermore, there’s no economic motive to synthesize this material for commercial use. Inexpensive yet gem-quality natural tourmalines are readily available. Although you can find so-called “synthetic tourmaline” for sale online, careful reading will reveal the term is usually used synonymously with “fake” or “simulated.” If the simulant is a lab-created material, vendors may claim the “tourmaline” itself is, thus, lab-created. In actuality, it’s not a tourmaline at all.
On the other hand, tourmalines can receive many enhancements. These can easily improve a low-quality stone’s appearance and color as well as change its natural color into something more attractive (and valuable).
Heating: lightens blue and green stones, common, stable, undetectable. Can produce other colors, rare, stable, undetectable.
Irradiation: produces red, deep pink, yellow, orange colors, and parti-colors, common. May fade on heating or prolonged exposure to bright light, undetectable.
Acid treatment: bleaches dark inclusions, primarily used on cat’s eyes, occasional, stable, undetectable.
Plastic or epoxy fillers: seal hollow tubes to prevent dirt from entering, occasional, stable. Detectable with hot point test and magnification.
The following sources are some of the major producers of tourmalines, and the varieties listed are some of the most notable from those sources. Many listed sources also produce additional varieties of tourmalines. Many other sources not listed also produce tourmalines.
At Nuristan, superb gem elbaite in shades of blue, pink, green, and even emerald green.
In Minas Gerais and other states, usually elbaite, in a huge variety of colors and sometimes large crystals; also bi-color, cat’s eye, watermelon tourmaline. Especially noteworthy are the immense cranberry-red crystals from the Jonas Lima Mine and the superb dark-red material from Ouro Fino.
At Kashmir, green elbaite crystals. RI 1.643, 1.622; SG = 3.05, birefringence = 0.021.
At Honshu, magnesio-foitite, rare.
Fine, deep red and other colors. The red is dravite; (also yellow shades). The following table describes their properties.
Liddicoatite (previously thought to be elbaite) in a huge range of colors, shades; crystals often concentrically zoned with many color zones, triangular in outline; many crystals very large. Also, fine rubellite.
New Jersey and New York: at Franklin and Hamburg, New Jersey, and at Gouverneur and DeKaIb, New York, uvite crystals, some with gem potential. This material had always been regarded as dravite.
At Chipata, dark red crystals similar to Kenyan dravite. RI 1.624-1.654; birefringence = 0.030; SG = 3.03-3.07 (average 3.05). Also gemmy yellow material with up to 9.2 wt. % MnO, very rare. Also, trapiche tourmalines.
Tourmalines weighing hundreds of carats have been cut out of material from various localities. Brazil and Mozambique produce some of the largest stones, but Maine and California have also yielded crystals of very large size. Most larger museums have fine tourmaline collections and display very large gems. (A representative collection of tourmaline colors would have to encompass well over 100 stones).
Private Collection: 258.08 (green cat’s eye); 256 (green, Maine, very large for locality).
Tourmaline rough can challenge even experienced gem cutters. Multi-colored gems are often weak where the colors meet, but all color varieties may have stressed areas. Nevertheless, once cut and set in jewelry, tourmalines are very durable stones.
Tourmaline’s Mohs hardness of 7 to 7.5 means these gems can resist scratches from most everyday hazards, including household dust. That’s very fortunate, because due to tourmaline’s electrical conductivity, these gems will attract more dust than non-conductive stones. So, you may have to clean them frequently
Since most tourmalines have numerous inclusions, avoid cleaning them with ultrasonic or steam devices. Vibrations and heat may cause liquid inclusions to expand, shattering the stone. Instead, use a soft brush, mild detergent, and warm water.