Rutile
Rutile is TiO2: tetragonal, hardness 6 to 6.5, density 4.23, adamantine. Five IMA rows share its formula, and brookite reads within 0.05 g of it in water.
Rutile is titanium dioxide, TiO2: tetragonal, hardness 6 to 6.5, density 4.23, adamantine to submetallic, with a pale brown streak and refractive indices near 2.6 and 2.9. It is grandfathered on the IMA list, 1803, Spain. The sheet calls it trimorphous with anatase and brookite; the September 2026 IMA list carries five TiO2 rows.
In short
- One formula, five IMA rows. A script over the September 2026 IMA-CNMNC Master List finds five rows written TiO2: rutile (G, 1803, Spain), anatase (A, 1962 s.p., France), brookite (G, 1825, United Kingdom), akaogiite (A, 2007, Germany) and srilankite (Rd, 2022 s.p., Sri Lanka), plus riesite written TiTiO4. The Handbook of Mineralogy rutile sheet names the two a collector meets: trimorphous with anatase and brookite.
- The TiO2 ladder, worked. A 20.00 g piece weighs 15.27 g in water as rutile, 15.10 to 15.22 g as brookite and 14.72 to 14.96 g as anatase, from the sheets’ densities. Rutile and brookite sit 0.05 g apart, inside the error of a kitchen scale: a documented negative for weighing. Streak and optics separate them better: rutile pale brown and uniaxial (+), anatase white to pale yellow and uniaxial (−), brookite white to greyish and biaxial (+).
- Rutilated quartz is quartz. The International Gem Society says rutile occurs as needle inclusions in quartz and agate and, as fibres in corundum, causes the star in star sapphires. Worked, 1% rutile by volume moves a 20.00 g quartz from 12.45 g to 12.50 g in water: the scale cannot see the needles; the eye can.
- Synthetic rutile was a diamond simulant. The gem society says it reached the gem market in 1948, grown by the Verneuil flame-fusion process, and was sold as Titania, but showed too much fire to convince. The sheet’s indices explain the fire: birefringence 0.286 to 0.296, worked. The diamond comparison is on is zircon a diamond.
- Fine crystals on the sheet: Graves Mountain, Georgia; Magnet Cove, Arkansas; Cavradi, Switzerland; Conquista and Ibitiara, Bahia, Brazil. It names no British locality. The anatase sheet names the Virtuous Lady mine, Devon, and both the anatase and brookite sheets name Fron Oleu near Tremadog, Wales.
| Name | IMA status, year, country | System (sheet) | Hardness | Density | 20.00 g piece in water | Streak | Optics |
|---|---|---|---|---|---|---|---|
| Rutile | G, 1803, Spain | Tetragonal | 6 to 6.5 | 4.23 (calc. 4.25) | 15.27 g | Pale brown, yellowish brown | Uniaxial (+), 2.605 to 2.613 and 2.899 to 2.901 |
| Brookite | G, 1825, United Kingdom | Orthorhombic | 5.5 to 6 | 4.08 to 4.18 | 15.10 to 15.22 g | White to greyish or yellowish white | Biaxial (+), 2.5831, 2.5843, 2.7004 |
| Anatase | A, 1962 s.p., France | Tetragonal | 5.5 to 6 | 3.79 to 3.97 | 14.72 to 14.96 g | White to pale yellow | Uniaxial (−), 2.5612 and 2.4880 |
| Akaogiite | A, 2007-058, Germany | No sheet used | - | - | - | - | TiO2 on the IMA list |
| Srilankite | Rd, 2022 s.p., Sri Lanka | No sheet used | - | - | - | - | TiO2 on the IMA list |
| Riesite | A, 2015-110a, Germany | No sheet used | - | - | - | - | Written TiTiO4 on the IMA list |
| Cassiterite (rutile group) | G, 1832, United Kingdom; SnO2 | Tetragonal | 6 to 7 | 6.98 to 7.01 | 17.13 to 17.15 g | Not compared here | Group mate, not a polymorph |
What is rutile? TiO2, as the sheet describes it
The names. The September 2026 IMA-CNMNC Master List lists rutile as TiO2, status G, grandfathered, 1803, with Spain as the country of first discovery. The Handbook sheet gives the same formula and places it in the rutile group; its name is from the Latin rutilus, red, a common colour of the mineral. On standard atomic weights TiO2 is 59.93% titanium by mass.
What it looks like, per the sheet. Tetragonal, point group 4/m 2/m 2/m. Crystals prismatic, elongated and striated parallel to [001], to 25 cm, showing {110} and {010} and terminated by {101} or {111}; also equant, rarely dipyramidal, and massive. Twinning on {011} is common, or on {031}: geniculated, reticulated, and as contact twins of two, six or eight individuals, cyclic, forms read from the rendered sheet. Colour reddish brown, red, pale yellow, pale blue, violet, rarely grass-green, and black if high in niobium and tantalum; streak pale brown to yellowish brown; lustre adamantine to submetallic. Cleavage {110} good, {100} moderate.
The Graves Mountain analysis. TiO2 97.46, Fe2O3 2.62: worked, 0.974 titanium and 0.026 iron per metal site. The sheet says measured density, 4.23, increases with Nb–Ta content. It also prints the single word photosensitive, with no further detail, and this page adds none.
Rutile, anatase or brookite? The TiO2 ladder
Method and count. Every line of the September 2026 IMA list, saved as text with pdftotext -layout, was parsed by script into name and formula (controls: the rutile, anatase, brookite, zircon and diamond rows must parse), and an independent scan of the formula column checked the result. Five rows are written TiO2: akaogiite, anatase, brookite, rutile and srilankite. Riesite is written TiTiO4, the same atoms doubled. The Handbook sheets cover the three a collector is likely to hold.
The ladder, worked. At 20.00 g: rutile 15.27 g in water, brookite 15.10 to 15.22 g, anatase 14.72 to 14.96 g. Documented negative: rutile and brookite are 0.05 g apart at their nearest, so the scale cannot separate them; anatase is at least 0.31 g lighter than rutile. The method is on how to measure specific gravity at home.
What separates them instead. System and habit: anatase is tetragonal, typically acute dipyramidal on its sheet; brookite orthorhombic, typically tabular and striated; rutile prismatic and striated. Optics: rutile uniaxial (+), anatase uniaxial (−), brookite biaxial (+). Streak: rutile pale brown, anatase white to pale yellow, brookite white to greyish white. Hardness does not help: rutile 6 to 6.5, the other two 5.5 to 6. Testing it properly is on how to test mineral hardness properly.
What is rutilated quartz?
Quartz with rutile inside it. The International Gem Society rutile article says rutile crystals occur as needle inclusions in a wide variety of gem materials, such as quartz and agate, and that rutile fibres in corundum cause asterism in stars such as star sapphires. Its rutilated quartz guide describes silky golden to brown inclusions, with colourless quartz the commonest host. The stone is quartz; the rutile is an inclusion, as tourmaline is in tourmalinated quartz on is tourmaline a quartz.
Worked: why the scale cannot see the needles. Quartz is 2.65 and rutile 4.23. A 20.00 g piece of quartz with 1% rutile by volume has a density of 2.666 and reads 12.50 g in water against 12.45 g for clean quartz; at 5%, 12.67 g. These are illustrative volumes, not measurements of any stone. The sheets agree on the pairing: quartz is on rutile’s Association line.
Synthetic rutile. The gem society says synthetic rutile reached the gem market in 1948, made by the Verneuil process, and was sold under the name Titania as a diamond simulant, until simulants such as cubic zirconia replaced it. It gives rutile a dispersion of 0.28, about six times diamond’s.
Where rutile is found: Graves Mountain, Magnet Cove and the Alps
The Distribution field opens many localities; a few for fine crystals and names: Cavradi, Tavetsch, Graubünden, and Lodrino, Tessin, Switzerland; the Pfitschtal, Trentino-Alto Adige, Italy; the Saualpe, and Herzogberg near Modriach, Styria, Austria; Kassoi Brod, Ural Mountains, Russia; Magnet Cove, Arkansas; Graves Mountain, Lincoln Co., Georgia; Stony Point, Alexander Co., North Carolina; Parkesburg, Chester Co., Pennsylvania; the Champion mine, Mono Co., California; large crystals from Conquista, and Ibitiara, Bahia, Brazil; and the Giftkuppe mine, Omaruru, Namibia.
In Britain the rutile sheet names nothing. The anatase sheet names the Virtuous Lady mine, Devonshire, and Fron Oleu near Tremadog, Wales; the brookite sheet names Fron Oleu too, and its first analysis is from Snowdon. Brookite is named for Henry James Brooke (1771–1857), English crystallographer, and the IMA list gives the United Kingdom as its country of first discovery.
Its company on the Association line: anatase, brookite, hematite, ilmenite, apatite, adularia, albite, titanite, chlorite, pyrophyllite, calcite, quartz. See hematite and the group mate cassiterite. 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.