Rutile

Rutile is a common mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the tetragonal crystal system with the chemical composition of TiO2 and developed mostly short to long prismatic, vertically striped crystals and very often in the form of polysynthetic twins crystal, lamellar and cyclic triplets and quadruplets, but also granular to massive mineral aggregates.

Most rutile crystals ranging in size from a few millimeters to a few centimeters. But it could also crystals of up to 25 cm length are found.

Special Features

Rutile may occur in different colors, often it is found but in reddish brown to bright red and black color. As inclusions ( inclusions) in other minerals - such as in quartz - rutile shines in strong golden yellow color and is referred to as Venus hair in this form and processed like to gemstones. Rarely, however, appear bluish or purple hues.

In feinnadeliger included to fibrous form, rutile ( light star) is responsible for, among other things occurring in sapphires and rubies asterism. In microscopic inclusions can next Hematite and other mineral inclusions emphasize the observed mainly in quartz "Phantom Crystals ".

Rutile is säureunlöslich and infusible before the blowpipe. In pure form, it is weakly paramagnetic with a specific magnetic susceptibility ( mass susceptibility ) of 7.7 • 10-7 emu / Oe • mg, it also contains iron, however, it is antiferromagnetic.

Etymology and history

Was described in 1803 by Abraham Gottlob Werner rutile, the rutilus named the mineral in accordance with its frequently occurring reddish color after the Latin word for red or reddish.

Until 1795, when its chemical composition was known, rutile was mistaken for a mineral of the tourmaline.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the rutile belonged to the mineral class of " oxides and hydroxides " and then to the Department of " oxides with the molar ratio of metal: oxygen = 1: 2", where he was named the " Rutilgruppe " formed with the other members Argutit, cassiterite, paratellurite, Plattnerit, pyrolusite and Tripuhyite.

The 9th edition used since 2001, valid and of the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the rutile also in the class of " oxides and hydroxides " and there in the department of " oxides with the molar ratio of metal: oxygen = 1: 2 and comparable " one. This division, however, is now further divided according to the size of the involved cations and the crystal structure, so that the mineral according to its composition and structure in the subdivision "With medium-sized cations: chains of edge-sharing octahedra " is to find where it together with Argutit, cassiterite, Plattnerit, pyrolusite, Tripuhyite, Tugarinovit and Varlamoffite the " rutile group " with the system no. 4.DB.05 forms.

The classification of minerals according to Dana assigns the rutile in the class of " oxides and hydroxides ," there though initially in the Department of " oxides " one. Here he is with Ilmenorutil, Struverit, pyrolusite, cassiterite, Plattnerit, Argutit, Squawcreekit and stishovite in the " Rutilgruppe ( Tetragonal: P4/mnm ) " with the system no. 04:04:01 within the subdivision "simple oxides with a cation charge of 4 ( AO2 ) ".

Modifications and varieties

Rutile is the most important and the only stable at high temperatures, modification of the titanium dioxide. The other two are of anatase and brookite.

Sagenit a Rutilvarietät is called, has the flat, line- up grid-like intergrowths of fine needle-like Rutilzwillingen.

Nigrin is the name for an iron-containing, black rutile.

Education and Locations

Rutile forms both magmatic metamorphic as well as high-temperature and high-pressure mineral and can be found as an accessory ingredient in many rocks, so including in river sediments. According to rutile is found associated with many other minerals, as besides the already mentioned further modifications anatase and brookite, you still adularia, albite, apatite, calcite, chlorite, ilmenite, pyrophyllite, titanite and quartz. With Hematite Rutile is also epitaxial adhesions.

Rutile occurs in eclogites and is the dominant Ti - phase in garnet amphibolites.

Worldwide, rutile far (as of 2011) are detected at around 3800 localities. Noteworthy for its exceptional mineral discoveries include the " Graves Mountain Mine " in the U.S. Lincoln County ( Georgia), in which up to 15 cm large crystals were revealed. In the " Cavradi Gorge " on the Gotthard massif and in the Brazilian municipalities Ibitiara (Bahia) and Itabira ( Minas Gerais ) were particularly beautiful rutile - hematite epitaxies on. Large knee or visor shaped crystal twins to about 7 cm in size were found in Golčův Jenikov and Soběslav in the Czech Republic.

In Germany rutile could especially in some regions of the Black Forest (Baden- Württemberg), in the Fichtelgebirge, Spessart, Bavarian Forest, Upper Palatinate Forest ( Bavaria ), Hesse, Lower Saxony, in the North Rhine -Westphalian Seven Mountains, the Eifel ( Rhineland -Palatinate ), in Saarland, be detected in the Saxon Erzgebirge, Schleswig -Holstein and Thuringia.

In Austria, found the mineral in Burgenland, in many regions of Carinthia, Salzburg and Styria, in some regions of Lower Austria and Tyrol and Upper Austria and Vorarlberg.

In Switzerland, rutile occurred mainly in the cantons of Graubünden, Ticino and Valais.

Other localities are Algeria, Angola, Antarctica, Argentina, Armenia, Australia, Azerbaijan, Ethiopia, Bangladesh, Belgium, Bolivia, Bulgaria, Burkina Faso, Burundi, Chile, China, Dominican Republic, Ecuador, Fiji, Finland, France, French Guiana, French Polynesia, Ghana, Greece, Greenland, Guatemala, Guyana, Haiti, Honduras, India, Indonesia, Iran, Ireland, Israel, Italy, Japan, Kazakhstan, Kenya, the sub-Antarctic Kerguelen, Kyrgyzstan, Colombia, the Democratic Republic of Congo, North and South Korea, Cuba, Lesotho, Luxembourg, Madagascar, Malawi, Malaysia, Malta, Morocco, Macedonia, Mexico, Mongolia, Mozambique, Myanmar, Namibia, Nepal, New Caledonia, New Zealand, Netherlands, Nigeria, Norway, Oman, Pakistan, Panama, Papua New Guinea, Paraguay, Peru, Philippines, Poland, Portugal, Reunion, Romania, Russia, Solomon Islands, Zambia, Saudi Arabia, Sweden, Serbia, Zimbabwe, Slovakia, Slovenia, Spain, Sri Lanka, South Africa, Sudan, Suriname, Taiwan, Tajikistan, Tanzania, Thailand, Chad, Czech Republic, Turkey, Uganda, Ukraine, Uzbekistan, Venezuela, the United Kingdom ( UK), the United States of America (USA), the U.S. Virgin Islands and Vietnam.

Even in rock samples of the Mid-Atlantic Ridge and the Southwest Indian Ridge and outside the Earth on the moon, or more precisely in the Fra Mauro Highlands rutile could be found.

In the West African state of Sierra Leone, 23% of global production capacities are (as of 2007), which probably also represent the largest reserves in the world with 259 million tons.

Morphology

Rutile often forms prismatic crystals along { 110 }, { 010 } and many others with dicksäuligem to feinnadeligem habitus, whose facets are stretched and streaked in parallel. Also ditetragonale prisms occur.

Twinning are generally encountered in rutile, which can be formed by two laws: Particularly frequently, twins, triplets and polysynthetic Much Linge in lamellar or cyclic form according to (101 ) in front, where the individuals abut each other at an angle of 65 ° 35 '. Characteristic are primarily knee or visor -shaped and V-shaped formation of twins. Less common are twins according to (301 ) in heart shape whose vertical axes meet at 54 ° 44 '. Both laws can occur simultaneously, thereby forming a grid-like or net-like units, which are referred to as Sagenit.

Cyclic Polyzwilling

Sagenit

" Rutile Alphabet "

Crystal structure

Rutile crystallized tetragonal in the space group P42/mnm ( Raumgruppen-Nr. 136) with the lattice parameters a = 4.59 Å and c = 2.96 Å and two formula units per unit cell.

The rutile structure is a frequently occurring type of structure for AB2 compounds and is based in contrast to the fluorite structure not based on a close packing of spheres. The oxide anions are indeed arranged in the manner of distorted and corrugated " hexagonal " layers, with half of the intervening octahedral sites are occupied by the Titan - cations, however, due to the tetragonal symmetry of this form corrugated layers no densest sphere packing. The crystal structure therefore can be better than a tetragonal rod packing of strands of edge-sharing [ TiO6 ] octahedra ( according to the Niggli notation: [ TiO4/2O2/1 ] ) describe that run parallel to the crystallographic c- axis. The strands are further linked via common corners to a three-dimensional [ TiO6 / 3] network, resulting in reduced the molecular formula TiO2 results. The octahedrally coordinated by oxygen atoms surrounding titanium cations thus have a coordination number of 6, while the oxide anions are surrounded by three titanium atoms in a slightly distorted trigonal planar arrangement ( coordination number 3).

A number of other inorganic compounds crystallizes in the rutile structure, including the oxides NbO 2, TAO2, MnO2 and SnO2 and the fluorides CRF2, MnF2, FeF2, COF2, NiF2, CuF 2 and ZnF 2.

Use

As a raw material

Rutile is a metal content of about 60% after the most important titanium ilmenite mineral.

Titanium dioxide in the rutile modification is used due to the high refraction as a white pigment. It also serves alone or in combination with cellulose as a sheath of electrodes for electric arc welding, which improves the welding or made possible.

Due to its semiconductor properties rutile found in the dye-sensitized solar cell, the so-called Grätzel cell use. Its band gap is about 3.0 eV, it may therefore absorb light less than about 400 nm, with a wavelength.

As a gemstone

Natural rutile is only occasionally processed by collectors for precious stones, as he trains mostly small crystals. Synthetic rutile, however, is since 1948 under the trade name " Titania " or " Diamont " (not to be confused with Diamondit! ) Sold as a diamond imitation, whereby it surpasses its luster by six times as high dispersion (fire) even far.

Happy to be processed into semi-precious stones enclosed in other minerals rutile needles, in addition to the golden glow for various optical effects such as asterism (star -shaped light reflections ) and chatoyancy ( cat's eye effect ) provide.