Tourmaline is one of our most popular gems. No other mineral comes in more colors and some of the combinations are in a class by themselves.
Tourmaline is readily available, which keeps prices reasonable. It is not until you get into large sizes, or extremely rare colors, that the prices go over a few hundred dollars per carat. Most colors are fairly common but pure blues and reds are rare and color-change is exceptionally rare.
You may also wish to visit the following articles:
- What do I look for when buying Chrome Green Tourmaline?
- What do I look for when buying Verdelite (green) Tourmaline?
- What do I look for when buying Rubellite Tourmaline?
- What do I look for when buying Indicolite Tourmaline?
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Varieties||Achroite, Chrome-Tourmaline, Dravite, Elbaite, Cuprian Elbaite, Paraíba Tourmaline, Fluor-buergerite, Indicolite, Liddicoatite, Rossmanite, Rubellite, Schorl, Uvite, Verdelite, Watermelon Tourmaline|
|Crystallography||Hexagonal (trigonal). Crystals common, usually long prismatic, heavily striated along length, various terminations; also equant, acicular.|
|Refractive Index||1.603 – 1.655|
|Specific Gravity||2.84 – 3.10. See table below.|
|Birefringence||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.|
|Stone Sizes||To very large|
|Luminescence||Tourmalines are usually weak to inert in UV light. 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.|
|Spectral||Not diagnostic; usually weak spectra observed.|
|Special Care Instructions||Multicolored gems are often weak where the colors meet|
|Transparency||Transparent to opaque|
|UV Long||Pink, inert to very weak red to violet. Other colors, generally inert.|
|UV Short||Pink, inert to very weak red to violet. Other colors, generally inert.|
|Absorption Spectrum||Blue and Green, near total absorption to 640 nm, strong narrow band at 498 nm. Red and Pink, broad band in green, lines at 458 and 451 nm.|
|Phenomena||Chatoyancy, color change|
|Identifying Characteristics||All, may contain hollow tubes, irregular threadlike liquid or gas inclusions, often in mesh like pattern. Cats Eye, dense concentration of hollow tubes.|
|Pleochroism||Moderate to strong, may be two shades of body color or two separate colors. Single colors are always stronger down the C axis.|
Comments by Donald Clark, CSM IMG
Tourmaline is a group of minerals that all have the same crystal structure, but vary in chemical make up, color, and other properties. Nine species are all you will find in older reference books. Fourteen are now known and there are still others being considered for new species.
Elbaite is the most common gem species, followed by schorl, dravite, and uvite. While rare, other species occasionally show up as gems as well. The properties of some species are so close that it is often difficult to make a distinction. For gemological purposes, it is sufficient to distinguish them all as tourmaline.
In most gemological literature, you will only find a limited range of properties for tourmaline. This is done to simplify the identification process. However, it has the significant disadvantage in that you cannot identify a gem that is not in your reference material.
Here is a complete range of properties for tourmaline:
|Natural &Lab created||7.5||7||3.90||2.82||1.820||1.603||.006 – .080||U –||.017|
Here is a breakdown of the properties by species. The ones most commonly used as gems are listed in bold italic type. Note that all tourmaline has the same hardness, optic sign, and dispersion.
|Species||SG high||SG low||RI high||RI low||Birefringence|
|Buergerite||3.32||3.29||1.735||1.655||.065 – .080|
|Dravite||3.90||3.10||1.675||1.604||.016 – .032|
|Schorl||3.24||2.82||1.698||1.620||.016 – .046|
|Tsiliaisite||~3.13||~3.13||1.648||1.622||.023 – .028|
|Uvite||3.01||3.09||1.660||1.612||.017 – .021|
- Buergerite: Dark brown to black crystals with bronze colored iridescence. Rare, found primarily in San Luis Potosi, Mexico.
- Chromdravite: Green to black. Rare, primary source is central Karelia, Russia.
- Dravite: Brown, black, greenish-black, dark red, and pale bluish-green to emerald green. Many sources.
- Elbaite: Most common tourmaline, with many sources. Comes in all colors.
- Tsiliaisite is a manganese-rich variety of Elbaite.
- Feruvite: Dark brown to black. Rare, primary source Cuvier Island, New Zealand.
- Foitite: Bluish-black, uncommon found primarily in California.
- Liddicoatite: Known for its complex multi-colored zoning. Uncommon, found primarily in Madagascar.
- Magnesiofoitite: Greenish brown, bluish gray. Rare, primary Honshu, Japan.
- Olenite: Pale pink. Rare, found primarily in Kola Peninsula, Russia.
- Povondraite: Also called Ferridravite. Black, nearly opaque. Rare, primary source Cochabamba, Bolivia.
- Rossmanite: Pink to tan. Rare, primary source Strázek Moldanubicum, Czech Republic.
- Schorl: Black, brown, blue or blue green. Common, many sources.
- Uvite: Black, green, brown, occasionally other colors. Common, several sources.
- Vanadiumdravite: Dark green to black.
- 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 cats eyes, occasional, stable, undetectable
- Plastic or Epoxy fillers, seals hollow tubes to prevent dirt from entering, occasional, stable, detect with hot point, magnification
Variety and Trade Names
- Achorite, colorless tourmaline
- Canary, bright yellow tourmaline from Malawi
- Cat’s Eye chatoyant tourmaline in a variety of colors
- Chrome tourmaline, colored by chromium, exhibits intense green coloring. Check with Chelsea filter; red or pink indicates chromium content.
- Color-Change distinct color change from daylight to incandescent light
- Dravite, often applied to yellow and brown tourmaline even if not of the dravite species
- Indicolite, blue tourmaline
- Paraíba, intense colors caused by copper. (See Paraíba for more detail.)
- Parti-Colored, having more than one color
- Rubellite, loosely applied to gems in the pink to red range, often strongly purplish, orangish, or brownish
- Verdelite, green tourmaline
- Watermellon, pink with a green border
- Brazilian emerald, green tourmaline
- Brazilian sapphire, blue tourmaline
- Ceylonese peridot, green tourmaline
Comments by Dr. Joel Arem
Tourmaline is a name applied to a family of related minerals, all having essentially the same crystal structure but varying widely in chemical composition, color, and properties. The nomenclature of tourmalines is complex because there are nine distinct mineral species in the group, as well as a wide variety of names that have been applied to specific color varieties. Tourmaline crystals are abundant worldwide, are sometimes large and well terminated, and often are cuttable.
Tourmaline is one of the most popular of gems among collectors because it is usually inexpensive and occurs in a vast array of colors. The colors are due to an almost unbelievable complexity of chemical composition, to which John Ruskin‘s quip (1890) still applies: “the chemistry of [tourmaline] is more like a mediaeval doctor‘s prescription than the making of a respectable mineral”. Schorl, the black tourmaline, was used in mourning jewelry during the Victorian era, a practice little used today. Such material is seldom seen in jewelry at all in modern times. Tourmaline crystals are often cracked and flawed, which puts a premium on clean gemstones, especially those over about 10 carats in size. The only acceptable types of inclusions are the tubes that, when densely packed, produce a chatoyancy and catseye effect in cabochons. The eye in catseye tourmalines can be very strong, set against a richly colored gem. Tourmalines occur in a wide enough range of colors to satisfy just about any fashion requirement. There is no cleavage, and the slight brittleness of the material is not a major problem in wear. Small tourmalines (under 5 carats) are fairly easy to obtain at modest cost. Very large, fine-colored stones are both rare and costly, however.
- Dravite: NaMg3Al6B3Si6O27(OH)3(OH,F)
- Uvite: CaMg3(Al5Mg)B3Si6O27(OH)3(OH,F)
- Elbaite: Na(Li,Al) 3Al6B3Si6O27 (OH)3(OH,F)
- Liddicoatite: Ca(Li,Al) 3Al6B3Si6O27(OH)3(OH,F)
- Buergerite: NaFe3Al6B3Si6O30F
- Chromdravite: NaMg3Cr6(BO3)3Si6,O18(OH)4
- Tsililisite: Na(Mn,Al)3Al6(BO3)3Si6O18(O,OH,F)4
- Ferridravite: (Na,K)(Mg,Fe+2)3Fe6+3(BO3)3Si6O18(O,OH)4
Tourmalines come in all colors from colorless to black. Crystals are frequently color zoned along their length (bicolor, tricolor, particolor, and so forth) or concentrically zoned (watermelon tourmaline). Dravite is usually black to brown, may be colorless. Uvite is black, brown, and green, usually dark colors. Schorl tends to be black, blue, or blue-green. Buergerite is always dark brown to black, with a bronze-colored iridescence or Schiller under the crystal surface. The gem tourmaline, elhaite, occurs in a huge range of colors and shades.
Liddicoatite is a relatively newly described species that was for years considered to be elbaite (from Madagascar) but when investigated turned out to be a calcium analogy of elbaite. Chromdravize, as might be expected, is an intense dark green color from the USSR. Gemmy, bright yellow manganiferous elbaite, close to tsilaisite in composition, has been found in Zambia.
Certain color varieties of tourmaline have widely used names. Achroite is colorless tourmaline; rubellite refers to pink and red shades, and blue tourmaline is generally referred to as indicolite.
The absorption of the 0-ray in tourmaline is strong enough to plane-polarize light. Sometimes this ray is totally absorbed and a tourmaline may appear to be isotropic because it shows only one absorption edge on the refractometer. Pleochroism is especially strong in dark green and brown tourmalines. 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.
Typical Pleochroic Colors for Tourmaline Species
|Buergerite||yellow-brown||very pale yellow|
|dark green||olive green|
|bluis green||yellowish green|
|medium to dark brown||yellowish to light brown|
|Elbaite||medium pink||light pink or colorless|
|green||yellow to olive green|
|blue-green||light green to purplish|
|blue||colorless to pink to purple|
|Ferridravite||dark brown to dark olive gree||light olive green to light brown|
like elbaite but type specimen is dark brown to light brown
|Schorl||blue to greenish blue||yellow, yellow-brown, pale violet or colorless|
|dark brown||yellow, light brown, or yellowish blue-green|
|Uvite (like dravite)|
|Source: From R.V. Dietrich, The Tourmaline Group, Van Nostrand Reinhold, New York, 1985, p.144; copyright 1985 by Van Nostrand|
Differentiated according to tourmaline color (approximate values):
- Pink and red: 3.01-3.06.
- Pale green: 3.05.
- Brown: 3.06.
- Dark green: 3.08-3.11.
- Blue: 3.05-3.11.
- Yellow-orange: 3.10.
- Black: 3.11—3. 12.
Tourmaline displays elongated or threadlike cavities, sometimes with two-phase inclusions. The tubes usually run parallel to the length of crystals and, when densely packed, may produce a chatoyant effect that yields catseye gems in cabochons. There may be gas-filled fractures in red tourmalines; also flat films that reflect light and appear black. Also: hornblende; mica crystals; apatite; zircon.
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.
- Sri Lanka: Yellow and brown crystals; this is the original source of gem tourmaline, now known to be uvite rather than dravite.
- Burma: The Mogok area produces red tourmalines, also some pink elbaites and brown uvites.
- Mursinka, Urals, USSR: also at Nerchinsk, blue, red, and violet crystals in a decomposed granite.
- Central Karelia, USSR: chromdravite (dark green).
- Brazil: In Minas Gerais and other states, usually elbaite, in a huge variety of colors and sometimes large crystals; also bicolor, catseye,watermelon tourmaline. Especially noteworthy are the immense cranberry-red crystals from the Jonas Lima Mine and the superb dark red material from Ouro Fino.
- Kashmir, India: Green elbaite crystals (refractive indices 1.643, 1.622; S.G. 3.05, birefringence 0.021).
- Nuristan, Afghanistan: superb gem elbaite in shades of blue, pink, green, even emerald green.
- Usakos, Namibia: Fine elbaite of rich green color (chrome tourmaline).
- Klein Spitzkopje, Otavi, Namibia: Tourmaline in many shades of green and other colors (elbaite).
- Zimbabwe: In the Somabula Forest area, fine elbaite.
- Mozambique: At Alta Ligonha, pale-colored elbaite in various shades; bicolors.
- Madagascar: 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.
- Tanzania: Elbaite containing Cr and V, resulting in rich green shades.
- Kenya: Fine, deep red and other colors; the red is dravite; (also yellow shades).
- Glenbuchat, Aberdeenshire, Scotland: color-zoned elbaite up to several cm, suitable for cutting.
- California: Elbaite in abundance at Pala and other localities, in both fine crystals and gemmy material. The pink elbaite from here is a unique pastel shade.
- Maine: At Newry, huge deposit of fine elbaite, with exquisite gem material in green, blue-green, blue, and pink to red colors.
- Connecticut: At Haddam, elbaite in small but fine crystals, color-zoned.
- Mexico: Buergerite occurs in rhyolite at San Luis Potosi.
- New York: New Jersey: 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.
- Zambia: At Chipata, dark red crystals similar to Kenyan dravite. lndices 1.624—1.654; birefringence = 0.030; S.G. = 3.03-3.07 (average 3.05). Also tsilaisite, gemmy yellow material with MnO up to 9.2%, very rare.
There are many other tourmaline localities, but the above are the major gem-producing ones.
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 crystals of very large size have been discovered. 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.
- Smithsonian Institution (Washington, D.C): 246 (pink, faceted egg, California); 116.2, 100 (pink, California); 172.7, 124.8 (champagne color, Mozambique); 122.9 (green, Mozambique); 117, 110 (green, Brazil); 110.8 (pink, USSR); 75 (rose-red. Brazil); 62.4 (pink, Brazil); 18.4 (pink, Maine); 103.8 (rose, Mozambique); 60 (blue-green, Brazil); 41.6 (brown, Sri Lanka); 23.5 (pale brown, Brazil); 17.9 (green, South Africa); 17.7 (yellow-green, Elba, Italy).
- Private Collection: 258.08 (green catseye); 256 (green, Maine— very large for locality).
Tourmaline is from the Singhalese word turamali, meaning mixed-colored stones because 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 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, director of the Gemological Institute of America. Chromdravite is named for its composition. Uvite is named after the Sri Lankan locality.