Tourmaline
Tourmaline is a group name: 42 IMA species share one borosilicate formula. Schorl, elbaite, dravite and the rest, hardness 7 to 7.5, and how to read a label.
Tourmaline is a group name, not a species. Counted by script, 42 rows on the September 2026 IMA list share its borosilicate formula, XY3Z6(T6O18)(BO3)3V3W. Black schorl, gem elbaite and brown dravite are three of them. All are hexagonal, hardness 7 to 7.5, density 2.90 to 3.22, and colour alone does not name one.
In short
- No mineral called plain tourmaline is on the September 2026 IMA-CNMNC Master List. The 2011 nomenclature (Henry and six co-authors, American Mineralogist 96, 895) defines the supergroup by the formula XY3Z6(T6O18)(BO3)3V3W. A label reading tourmaline is a group determination.
- 42 species, counted by formula, not by name. Tourmaline names share no suffix, so we counted IMA rows whose formula has a six-membered T6O18 ring followed by (BO3)3. The script finds 42, and a plain-text search for the same string finds the same 42 lines. Status: 32 approved, 6 redefined, 2 grandfathered (dravite, elbaite), 2 renamed (schorl, povondraite).
- The X site sorts them into three groups, as the 2011 report sets out: alkali, calcic and X-vacant. Among the 42 that is 27 alkali (26 sodium, 1 potassium), 8 calcic and 7 vacant. The W site, at the end of the formula, adds fluor- and oxy- names: 14 hydroxyl, 8 fluorine and 20 oxygen.
- Colour does not name a tourmaline. Of the seven Handbook sheets used here, five list black (schorl, dravite, uvite, foitite and feruvite), and four list green and four red. Elbaite, the lithium species, is not black on its sheet; schorl is only black.
- Hardness 7 to 7.5 is high for this site’s reference set. Of the 168 sheets that print a hardness, 12 reach 7, schorl and uvite among them, and 3 reach 7.5: corundum, topaz and uvite.
| Handbook sheet | IMA name and formula | IMA status, year, country | X-site group | Hardness | Density (measured) | Colour on the sheet | Crystals to |
|---|---|---|---|---|---|---|---|
| Schorl | Schorl, NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH) | Rn; 2007 s.p.; Germany | Alkali | 7 | 3.18 to 3.22 | Black, brownish black, bluish black | 1.5 m |
| Elbaite | Elbaite, Na(Al1.5Li1.5)Al6(Si6O18)(BO3)3(OH)3(OH) | G; 1913; Italy | Alkali | 7 | 2.90 to 3.10 | Green, blue, red, orange, yellow, colourless; often zoned | 1.6 m |
| Dravite | Dravite, NaMg3Al6(Si6O18)(BO3)3(OH)3(OH) | G; 1884; Slovenia | Alkali | 7 | 3.03 to 3.18 | Brown to black, red, yellow, blue, green, colourless, white | 20 cm |
| Uvite | Uvite, CaMg3(Al5Mg)(Si6O18)(BO3)3(OH)3(OH) | A; 2019-113; Italy | Calcic | 7.5 | 2.97 to 3.14 | Brown, light to dark green, red, black | 15 cm |
| Liddicoatite | Fluor-liddicoatite, Ca(Li2Al)Al6(Si6O18)(BO3)3(OH)3F | Rd; 1976-041; Madagascar | Calcic | 7.5 | 3.02 | Brown, green, pink, red, blue; zoned | 25 cm |
| Feruvite | Feruvite, CaFe2+3(Al5Mg)(Si6O18)(BO3)3(OH)3(OH) | A; 1987-057; New Zealand | Calcic | About 7 | 3.207 | Dark brown-black | 2 mm grains |
| Foitite | Foitite, ☐(Fe2+2Al)Al6(Si6O18)(BO3)3(OH)3(OH) | A; 1992-034; USA | X-vacant | About 7 | 3.17 | Bluish black | 5.5 cm |
Is tourmaline a mineral? It is a supergroup of 42 species
The formula, from the 2011 report: XY3Z6(T6O18)(BO3)3V3W. X is sodium, calcium, potassium or a vacancy; Y is iron, magnesium, manganese, aluminium, lithium or chromium; Z mostly aluminium; T silicon, with some aluminium or boron; V is hydroxyl or oxygen; W is hydroxyl, fluorine or oxygen. Species are named by the dominant ion of the dominant valence at each site. Where hydroxyl and fluorine compete at W, the hydroxyl species keeps the root name and the other takes a prefix: dravite and fluor-dravite.
How we counted, and why not by name. Microlite-group names all end in -microlite; tourmaline names do not share an ending. So the script parsed every row of the September 2026 IMA-CNMNC Master List and kept those whose formula contains a T6O18 ring immediately followed by (BO3)3. It finds 42 rows. As an independent check, a plain-text search of the list for O18)(BO3)3 finds 42 lines, the same 42. Every formula with fluorine has it in the last position, the W site. Three other borate rows with (BO3)3 (gaudefroyite, karlite, sakhaite) have no ring and are excluded.
This page is filed under tourmaline deliberately, because that is the word on most labels. The axinite, microlite and apatite pages treat their group names the same way. The live uvite page covers that name’s own redefinition.
Schorl, elbaite or dravite? What the label can and cannot tell you
Read the X and Y sites, not the colour. Schorl is sodium and ferrous iron at Y, elbaite sodium with lithium and aluminium, dravite sodium and magnesium, uvite calcium and magnesium. The sheets show how far colour overlaps: dravite is listed brown to black, red, yellow, blue, green, colorless, white. Elbaite and dravite form a series, and so do schorl and dravite.
Worked on the Handbook’s Dobrawa, Slovenia, dravite analysis: X is Na0.73 K0.12 Ca0.07, so sodium, the alkali group. Y is Mg2.70 against Al0.35 and Mn0.08, so magnesium: dravite. The Elba elbaite gives X Na0.74 and Y Al2.11 Li1.05: lithium and aluminium, elbaite.
Worked on the liddicoatite sheet, where the name has moved. The Antsirabe, Madagascar, analysis has X Ca0.72 against Na0.27, so calcic. Its anions are (OH)2.86 F0.87 O0.27 over the four V+W positions. Filling the three V positions first with hydroxyl and oxygen, as the IMA formulas place them, leaves F0.87 at W: fluorine-dominant. The September 2026 list gives the 1976-041 number and Madagascar to fluor-liddicoatite. Plain liddicoatite is now a hydroxyl species, IMA 2025-047, from the Czech Republic. A pre-2025 liddicoatite label on Madagascar material therefore most probably describes what is now called fluor-liddicoatite. That is our reading of the two sources, not a published reassignment of any specimen.
Why tourmaline crystals look the way they do
Point group 3m, on every sheet used here. Prisms are striated parallel to [0001] and cross-sections are typically triangular with curved, convex sides, as the dravite and uvite sheets put it. Schorl and elbaite crystals are commonly hemimorphic: the two ends carry different faces, which is covered on what is a double terminated crystal. The sheets record crystals to 1.6 m for elbaite and 1.5 m for schorl.
Zoning is recorded, not a defect. Elbaite’s sheet records zoning common parallel to trigonal outline; liddicoatite’s, zoning parallel to pyramid faces. The USGS gemstone list gives the trade names rubellite, pink to red, and indicolite, dark blue. They are colour names, not species: neither is on the IMA list.
Hardness is a clean field test. At 7 to 7.5 a tourmaline is at least as hard as quartz (7 on its sheet), and harder than calcite at 3 and the calcium apatites at 5. Of the 168 sheets in the set that print a hardness, 12 reach 7: cassiterite, corundum, epidote, fayalite, forsterite, grossular, quartz, schorl, topaz, uvite, vesuvianite and zoisite. The method is on how to test mineral hardness properly.
Where tourmaline is found, including Devon
Schorl: many localities, but few for fine crystals. The sheet names Sonnenberg near St. Andreasberg, Harz; Bovey Tracey, Devon; San Piero in Campo, Elba; Alabashka and Mursinka, Urals; Haddam, Connecticut; Stony Point, North Carolina; the Little Three mine, Ramona, California; Minas Gerais, Brazil; Namibia; and Nuristan, Afghanistan. It occurs in granites and granite pegmatites, high-temperature hydrothermal veins and some metamorphic rocks.
Elbaite: San Piero in Campo, Elba; the Yekaterinburg district, Urals; Laghman Province, Afghanistan; Gilgit, Pakistan; Madagascar; Alto Ligonha, Mozambique; Mt. Mica and Newry, Maine; the Pala and Mesa Grande districts, California; and Minas Gerais and Paraíba, Brazil. Dravite and uvite both list Franklin and Hamburg, Sussex Co., New Jersey (Franklin and Sterling Hill), Gouverneur in St. Lawrence Co., New York, and Brumado, Bahia.
Against the 176 sheets in the set, the word tourmaline appears on 8 sheets, and tourmaline, schorl or elbaite is named in the Association field of 8. Those 8 include cassiterite, muscovite, lepidolite and orthoclase: the pegmatite and greisen assemblage. The rest of the reference section is at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.