Rutile

Rutile is a mineral composed primarily of titanium dioxide (TiO2). It is one of the three main minerals of titanium, along with ilmenite and leucoxene. Rutile is commonly found in igneous rocks, metamorphic rocks, and certain types of sedimentary rocks. It is a common accessory mineral in many ore deposits and is often associated with minerals such as magnetite, hematite, and zircon.

Quartz with Rutile, Novo Horizonte, Bahia, Northeast Region, Brazil
Rutile in quartz from Itabira, Brazil. Bristol City Museum and Art Gallery.

The name “rutile” is derived from the Latin word “rutilus,” which means “reddish.” This is because rutile can occur in various colors, including reddish-brown, black, yellow, and golden, depending on impurities present in the mineral. The crystal structure of rutile is tetragonal, with elongated prismatic crystals that are often striated.

Rutile has several important industrial applications due to its high refractive index and strong resistance to heat and chemical corrosion. One of its main uses is as a pigment in paints, plastics, ceramics, and other materials. It imparts a bright white color and excellent opacity to these products. Rutile is also used as a source of titanium metal, which has a wide range of applications in industries such as aerospace, automotive, electronics, and medical devices.

In addition to its industrial uses, rutile is valued as a collector’s mineral and gemstone. Transparent rutile crystals are sometimes cut and polished for use as gemstones. These specimens, known as “rutilated quartz,” display fine needle-like rutile inclusions that create unique and visually striking patterns within the quartz.

Rutile deposits are found worldwide, with significant reserves located in Australia, South Africa, India, and several other countries. The extraction of rutile typically involves mining operations, followed by processing to separate the mineral from other impurities. The processed rutile is then utilized in various industries according to its intended applications.

Overall, rutile is an important mineral with diverse uses, ranging from industrial applications to ornamental purposes. Its unique properties and widespread occurrence make it a valuable resource in numerous fields.

Rutile has one of the highest refractive indices at the real wavelengths of all known crystals, and also has very high birefringence and high dispersion. With these properties, it is possible to produce certain optical elements, especially polarized optics, for infrared and infrared wavelengths longer than about 4.5.

Natural Rutile can contain up to 10% iron and large amounts of niobium and tantalum. Ruthyl was first described in 1803 by Abraham Gottlob Werner.

Name: From the Latin rutilus, red, in allusion to the color

Association: Anatase, brookite, hematite, ilmenite, apatite, adularia, albite, titanite, chlorite, pyrophyllite, calcite, quartz

Polymorphism & Series: Trimorphous with anatase and brookite

Mineral Group: Rutile group.

Diagnostic Features: Characterized by its peculiar adamantine luster and red color. Lower specific gravity distinguishes it from cassiterite.

Composition: Titanium dioxide, Ti02. Ti = 60 per cent, 0 = 40 per cent. A little iron is usually present and may amount to 10 per cent.

Crystallography: Tetragonal; ditetragonal-dipyramidal. Prismatic crystals with dipyramid terminations common (Fig. 315). Vertically striated. Frequently in elbow twins, often repeated (Figs. 316 and 317). Twinning plane is dipyramid of second order {Oil}. Crystals frequently slender acicular. Also compact massive.

Contents

• Chemical composition and crystal structure
• Chemical Properties
• Rutile Physical Properties
• Rutile Optical Properties
• Formation and Geologic Occurrence
• Industrial Applications of Rutile
• Rutile as a Gemstone
• Rutile Synthesis and Production
• Rutile in Jewelry and Fashion
• Distribution
• References

Chemical composition and crystal structure

The chemical composition of rutile is titanium dioxide (TiO2). It consists of one titanium atom bonded to two oxygen atoms, resulting in a ratio of 1:2.

Regarding its crystal structure, rutile belongs to the tetragonal crystal system. The crystal structure of rutile is based on a lattice arrangement of titanium and oxygen atoms. Each titanium atom is surrounded by six oxygen atoms, forming octahedral coordination. The oxygen atoms are positioned at the corners of the octahedron, while the titanium atom is located in the center. This arrangement creates a three-dimensional framework of interconnected octahedra.

The unit cell of rutile consists of two formula units (TiO2) and has a unique structure. It is characterized by elongated prismatic crystals with a distinct striated pattern. The striations, or parallel lines, are often observed on the crystal faces and result from the growth patterns during the mineral’s formation.

The crystal lattice of rutile is relatively rigid and stable, contributing to its resistance to heat, light, and chemical corrosion. This stability is advantageous in various applications, such as its use as a pigment and in the production of optical components.

It is important to note that while rutile is the most common and well-known form of titanium dioxide, there are other polymorphs of TiO2, including anatase and brookite. These polymorphs have different crystal structures and physical properties. Rutile is the most thermodynamically stable form at normal temperature and pressure conditions, while anatase and brookite are metastable forms that can transform into rutile over time under certain conditions.

Chemical Properties

Rutile, with the chemical formula TiO2, exhibits several important chemical properties:

1. Composition: Rutile is composed of titanium and oxygen atoms, with a ratio of one titanium atom to two oxygen atoms.
2. Stability: Rutile is a stable compound and is resistant to heat, light, and chemical corrosion. It retains its structural integrity under normal conditions.
3. Refractivity: Rutile has a high refractive index, which means it bends and slows down light more than many other materials. This property makes it valuable in the production of optical lenses, prisms, and high-quality glass.
4. Insolubility: Rutile is insoluble in water and most acids, including strong acids. It is also resistant to alkaline solutions.
5. Photocatalytic Properties: Rutile exhibits photocatalytic activity, meaning it can initiate chemical reactions under the influence of light. This property has led to its use in applications such as solar cells, wastewater treatment, and self-cleaning surfaces.
6. Redox Reactions: Rutile can participate in redox reactions, where it can either gain or lose electrons. For example, it can be reduced to titanium metal by reacting it with certain reducing agents.
7. Crystal Structure: Rutile has a tetragonal crystal structure, with titanium atoms arranged in octahedral coordination. The arrangement of atoms gives rutile its characteristic properties and shapes its physical and chemical behavior.

These chemical properties contribute to the diverse range of applications of rutile in various industries, including pigments, ceramics, optics, electronics, and more.

Rutile Physical Properties

Color	Blood red, brownish yellow, brown-red, yellow, greyish-black, black, brown, bluish or violet
Streak	Greyish black, pale brown, light yellow
Luster	Adamantine, Metallic
Cleavage	Distinct/Good {110} distinct, {100} less distinct; and, {111} in traces.
Diaphaneity	Transparent
Mohs Hardness	6 – 6,5
Crystal System	Tetragonal
Tenacity	Brittle
Density	4.23(2) g/cm3 (Measured)    4.25 g/cm3 (Calculated)
Fracture	Irregular/Uneven, Conchoidal, Sub-Conchoidal
Parting	On {092} due to twin gliding; also on {011}.
Other characteristics	Strongly anisotropic
Crystal habit	Acicular to Prismatic crystals, elongated and striated parallel to [001]

Rutile Optical Properties

Type	Anisotropic
Anisotropism	Strong
Color / Pleochroism	Distinct; red, brown, yellow, green.
RI values:	nω = 2.605 – 2.613 nε = 2.899 – 2.901
Twinning	Common on {011}, or {031}; as contact twins with two, six, or eight individuals, cyclic, polysynthetic
Optic Sign	Uniaxial (+)
Birefringence	δ = 0.294
Relief	Very High
Dispersion:	Strong

Formation and Geologic Occurrence

Rutile forms through a variety of geologic processes and can be found in different geological settings. Here is an overview of its formation and geologic occurrence:

1. Magmatic Differentiation: Rutile can crystallize from magmas during the cooling and solidification of igneous rocks. Titanium-rich magmas, such as those associated with anorthosite and norite, provide favorable conditions for the formation of rutile. As the magma cools, minerals start to crystallize, and rutile can precipitate along with other minerals, such as quartz and feldspar.
2. Metamorphic Processes: Rutile commonly forms during regional or contact metamorphism, which involves high temperatures and pressures. During these processes, pre-existing minerals undergo transformations and recrystallization. Under the right conditions, minerals like ilmenite and titanite can undergo metamorphic reactions and produce rutile as a stable phase.
3. Hydrothermal Processes: Hydrothermal fluids, which are hot, mineral-rich solutions, can transport and deposit rutile in veins and fractures within rocks. These fluids are typically associated with igneous activity and can introduce titanium and oxygen into the rock formations. As the hydrothermal fluids cool and precipitate minerals, rutile can form along with other minerals in hydrothermal veins.
4. Placer Deposits: As mentioned earlier, rutile can be concentrated in placer deposits through weathering, erosion, and sedimentation processes. Over time, heavy minerals, including rutile, can be transported by water and accumulate in riverbeds, beaches, and coastal areas. The mechanical sorting action of water helps separate the denser rutile grains from lighter minerals, leading to their concentration in placer deposits.
5. Weathering and Sedimentary Processes: Weathering of primary rocks and subsequent erosion can release rutile into the sedimentary system. The detrital rutile can be transported by rivers, streams, and wind and eventually deposited in sedimentary basins. In sedimentary rocks, rutile grains can be found in sandstones, conglomerates, and other sedimentary formations.

It is important to note that the specific geological conditions and processes of rutile formation may vary depending on the location and geological history of a particular region. Rutile occurrences are often associated with other minerals such as ilmenite, zircon, magnetite, and various silicate minerals. Understanding the geological context and formation processes is crucial for the exploration and extraction of rutile deposits.

Industrial Applications of Rutile

Rutile has several important industrial applications due to its unique properties and characteristics. Some of the main industrial applications of rutile include:

1. Pigments: Rutile is widely used as a white pigment in paints, coatings, plastics, and paper. Its high refractive index and excellent opacity provide bright white color and good hiding power. Rutile pigments are known for their durability, weather resistance, and chemical stability, making them suitable for outdoor applications.
2. Ceramics: Rutile is utilized in the ceramics industry as an opacifier and a flux. It imparts opacity to ceramic glazes, allowing for vibrant and consistent colors. Rutile is also used as a fluxing agent in the production of ceramic bodies, helping to lower the melting point and improve the flow of the materials during firing.
3. Refractories: Rutile’s high melting point, thermal stability, and resistance to chemical corrosion make it valuable in the production of refractory materials. Refractories made with rutile can withstand high temperatures and harsh environments, making them suitable for applications in furnaces, kilns, and other high-temperature processes.
4. Welding Electrodes: Rutile is commonly used as a coating material for welding electrodes. The rutile coating provides stability and improves the arc characteristics during welding, ensuring a smooth and controlled welding process. The presence of rutile also contributes to the mechanical strength and quality of the welded joints.
5. Catalysts: Rutile exhibits photocatalytic properties, meaning it can initiate chemical reactions under the influence of light. This property is utilized in various environmental and energy applications, such as photocatalytic water splitting for hydrogen production, photovoltaic devices, and air purification systems.
6. Optics: Rutile’s high refractive index and transparency in the visible and near-infrared regions of the electromagnetic spectrum make it valuable in the production of optical components. Rutile is used in lenses, prisms, and polarizers for applications in cameras, microscopes, telescopes, and other optical instruments.
7. Electrodes and Electronic Components: Rutile can be processed into thin films and used as electrodes in electronic devices such as sensors, capacitors, and memory devices. It has good electrical conductivity and stability, making it suitable for these applications.

These are just some of the prominent industrial applications of rutile. Its unique combination of properties, including high refractive index, thermal stability, and chemical resistance, makes it a versatile and valuable material in various industries.

Rutile as a Gemstone

Rutile is also valued as a gemstone due to its unique inclusions and optical properties. The most common gemstone form of rutile is known as “rutilated quartz,” which consists of transparent quartz with needle-like rutile inclusions. These inclusions can vary in color, typically appearing golden, reddish-brown, or black.

The rutile inclusions in rutilated quartz create visually striking patterns and add beauty and interest to the gemstone. The fine and delicate needles of rutile can be distributed randomly or form organized patterns within the quartz, resembling rays, stars, or threads. These patterns are highly sought after by gemstone collectors and jewelry enthusiasts.

The optical effect caused by the rutile inclusions is known as chatoyancy or the “cat’s eye effect.” When properly cut and polished, rutilated quartz can exhibit a captivating chatoyant band that appears as a bright, shimmering line moving across the surface of the gemstone. This effect is caused by the reflection of light from the aligned rutile needles within the quartz.

Rutilated quartz is often used in various types of jewelry, including rings, pendants, earrings, and bracelets. It is typically cut into cabochons or faceted stones to showcase the unique inclusions and maximize their visual impact. The golden and reddish-brown varieties of rutilated quartz are especially popular due to their warm and eye-catching appearance.

In addition to rutilated quartz, other gemstones may also contain rutile as inclusions, although they are less common. These include rutile tourmaline and rutile topaz, where rutile needles are present within the crystal structures of these gemstones.

As with any gemstone, the value of rutilated quartz is influenced by factors such as clarity, size, color, and the quality and visibility of the rutile inclusions. Gems with well-defined, abundant, and evenly distributed rutile inclusions are generally considered more desirable.

Rutile as a gemstone offers a unique and visually appealing option for those seeking gemstones with distinctive characteristics and natural beauty. Its unusual inclusions and optical effects make rutilated quartz a fascinating choice for jewelry and gemstone enthusiasts.

Rutile Synthesis and Production

Rutile can be synthesized and produced through various methods, including both natural processes and laboratory techniques. Here are some common methods used for rutile synthesis and production:

1. Natural Formation: Rutile can naturally form through geological processes, as discussed earlier. It can crystallize from magmas during the cooling and solidification of titanium-rich igneous rocks. Additionally, metamorphic processes, hydrothermal activities, and weathering can contribute to the formation of rutile in natural settings over long periods of time.
2. Mineral Extraction and Processing: Rutile is commercially produced by mining and processing mineral deposits that contain significant amounts of rutile. The extraction process involves mining operations to access rutile-bearing ores, followed by various beneficiation techniques to separate rutile from other minerals and impurities. These techniques may include crushing, grinding, gravity separation, magnetic separation, and flotation.
3. Chemical Synthesis: Rutile can be synthesized in the laboratory using chemical methods. One common approach is the hydrolysis of titanium compounds, such as titanium chloride or titanium alkoxides, in the presence of appropriate reagents and conditions. This process allows for the controlled formation of rutile nanoparticles or larger rutile crystals.
4. Sol-Gel Method: The sol-gel method is another technique used for the synthesis of rutile. It involves the hydrolysis and condensation of precursor materials, typically metal alkoxides, to form a sol or gel-like solution. The sol or gel is then subjected to heat treatment to transform it into the desired rutile phase. This method allows for the production of rutile with controlled particle size, morphology, and crystallinity.
5. Vapor Deposition Techniques: Rutile can be produced through vapor deposition techniques such as chemical vapor deposition (CVD) and physical vapor deposition (PVD). These methods involve the introduction of precursor gases or vapor onto a substrate, where the rutile phase forms through chemical reactions or condensation. Vapor deposition techniques are often used to create thin films or coatings of rutile for various applications.

The specific synthesis method used for rutile production depends on the desired characteristics, particle size, and application requirements. Natural mineral deposits remain the primary source of commercial rutile, while laboratory synthesis methods are employed for specific research, engineering, and manufacturing purposes.

It’s worth noting that while rutile is an important mineral and widely available, its synthesis and production can be complex and require careful control of various parameters to achieve the desired quality and properties.

Rutile in Jewelry and Fashion

Rutile, particularly in the form of rutilated quartz, has gained popularity in the world of jewelry and fashion due to its unique and captivating appearance. Here’s how rutile is used in jewelry and fashion:

1. Rutilated Quartz Jewelry: Rutilated quartz is a popular gemstone used in various types of jewelry. The golden, reddish-brown, or black rutile inclusions within the transparent quartz create eye-catching patterns and add visual interest to the gemstone. Rutilated quartz is often cut into cabochons or faceted stones and used in rings, pendants, earrings, and bracelets. It is appreciated for its natural beauty and the chatoyant effect caused by the aligned rutile inclusions.
2. Statement Pieces: Rutile in jewelry is often used to create bold and statement pieces. The striking patterns and unique inclusions of rutilated quartz make it a centerpiece gemstone that stands out and captures attention. Jewelry designers incorporate rutilated quartz into large cocktail rings, dramatic pendants, and other statement pieces to create a visually impactful look.
3. Bohemian and Natural Styles: Rutile in jewelry complements bohemian and natural fashion styles. The earthy and organic look of rutilated quartz, with its golden or reddish-brown rutile inclusions, resonates well with the boho aesthetic. It is often used in combination with other natural materials like wood, leather, or woven fibers to create eclectic and free-spirited jewelry designs.
4. Fashion Accessories: Rutile can be utilized beyond traditional jewelry and incorporated into fashion accessories. Designers incorporate rutilated quartz into belt buckles, hairpins, cufflinks, and other fashion accessories to add a touch of natural beauty and uniqueness. The golden or reddish-brown rutile inclusions create an appealing contrast against various materials, making these accessories visually striking.

When wearing rutile jewelry or fashion accessories, it’s important to consider the stone’s care and maintenance. Like other gemstones, rutile should be protected from sharp blows, chemicals, and extreme temperatures to maintain its appearance and durability. Regular cleaning and proper storage are also recommended to preserve the beauty and longevity of rutile jewelry.

Rutile’s distinctive appearance and metaphysical associations make it a sought-after choice for those seeking jewelry and fashion items that are visually appealing and hold deeper meaning.

Distribution

Rutile is distributed worldwide, with significant deposits found in various countries across different continents. Here are some regions known for their rutile distribution:

• Australia: Australia is one of the largest producers of rutile. Major rutile deposits are found in Western Australia, Queensland, and New South Wales. The Murray Basin in Victoria is particularly renowned for its extensive rutile resources.
• South Africa: South Africa is another prominent producer of rutile. The mineral is found in the coastal regions of KwaZulu-Natal and the Eastern Cape. The Richards Bay Minerals (RBM) operation in KwaZulu-Natal is a significant source of rutile in the country.
• India: India is known for its rutile resources, particularly in the coastal regions of Odisha, Tamil Nadu, and Kerala. These areas host substantial deposits of heavy minerals, including rutile.
• Sierra Leone: Sierra Leone has significant rutile deposits along its coastline. The Sierra Rutile Mine in the southwestern part of the country is a major rutile mining operation.
• Ukraine: Ukraine is home to substantial rutile resources, particularly in the region of Zhytomyr and Volyn. The deposits in these areas are associated with titanium-rich igneous rocks.
• Brazil: Brazil has rutile deposits located in various states, including Minas Gerais, Rio de Janeiro, and Bahia. The Alto Horizonte Mine in Minas Gerais is an important rutile producer in the country.
• Other Countries: Rutile deposits can also be found in several other countries, including the United States (primarily in Florida and Virginia), Madagascar, Mozambique, China, Sri Lanka, Norway, Canada, and many more.

It’s important to note that the distribution and abundance of rutile deposits can vary within each country, and ongoing exploration efforts may uncover new sources in previously unexplored regions. The availability of rutile in different areas contributes to its global supply for various industrial and commercial purposes.

References

• Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
• Dana, J. D. (1864). Manual of Mineralogy… Wiley.
• Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
• Mindat.org. (2019): Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].
• Wikipedia contributors. (2019, June 10). Rutile. In Wikipedia, The Free Encyclopedia. Retrieved 22:06, June 30, 2019, from https://en.wikipedia.org/w/index.php?title=Rutile&oldid=901162262