Rutile
Rutile is a mineral composed of titanium dioxide. Rutile is the most common natural form of TiO2. Other rarer polymorphs of TiO2 are known including anatase, brookite. Rutile has one of the highest refractive indices at visible wavelengths of any known crystal and exhibits a large birefringence and high dispersion. Owing to these properties, it is useful for the manufacture of certain optical elements polarization optics, for longer visible and infrared wavelengths up to about 4.5 μm. Natural rutile may contain up to significant amounts of niobium and tantalum. Rutile derives its name from the Latin rutilus, red, in reference to the deep red color observed in some specimens when viewed by transmitted light. Rutile was first described in 1803 by Abraham Gottlob Werner. Rutile is a common accessory mineral in high-temperature and high-pressure metamorphic rocks and in igneous rocks. Thermodynamically, rutile is the most stable polymorph of TiO2 at all temperatures, exhibiting lower total free energy than metastable phases of anatase or brookite.
The transformation of the metastable TiO2 polymorphs to rutile is irreversible. As it has the lowest molecular volume of the three main polymorphs, it is the primary titanium bearing phase in most high-pressure metamorphic rocks, chiefly eclogites. Within the igneous environment, rutile is a common accessory mineral in plutonic igneous rocks, though it is found in extrusive igneous rocks those such as kimberlites and lamproites that have deep mantle sources. Anatase and brookite are found in the igneous environment as products of autogenic alteration during the cooling of plutonic rocks; the occurrence of large specimen crystals is most common in pegmatites and granite greisens. Rutile is found as an accessory mineral in some altered igneous rocks, in certain gneisses and schists. In groups of acicular crystals it is seen penetrating quartz as in the fléches d'amour from Graubünden, Switzerland. In 2005 the Republic of Sierra Leone in West Africa had a production capacity of 23% of the world's annual rutile supply, which rose to 30% in 2008.
Rutile has a tetragonal unit cell, with unit cell parameters a = b = 4.584 Å, c = 2.953 Å. The titanium cations have a coordination number of 6, meaning they are surrounded by an octahedron of 6 oxygen atoms; the oxygen anions have a coordination number of 3. Rutile shows a screw axis when its octahedra are viewed sequentially. Rutile crystals are most observed to exhibit a prismatic or acicular growth habit with preferential orientation along their c axis, the direction; this growth habit is favored as the facets of rutile exhibit the lowest surface free energy and are therefore thermodynamically most stable. The c-axis oriented growth of rutile appears in nanorods and abnormal grain growth phenomena of this phase. In large enough quantities in beach sands, rutile forms an important constituent of heavy minerals and ore deposits. Miners extract and separate the valuable minerals – e.g. rutile and ilmenite. The main uses for rutile are the manufacture of refractory ceramic, as a pigment, for the production of titanium metal.
Finely powdered rutile is a brilliant white pigment and is used in paints, paper and other applications that call for a bright white color. Titanium dioxide pigment is the single greatest use of titanium worldwide. Nanoscale particles of rutile are transparent to visible light but are effective in the absorption of ultraviolet radiation; the UV absorption of nano-sized rutile particles is blue-shifted compared to bulk rutile, so that higher-energy UV light is absorbed by the nanoparticles. Hence, they are used in sunscreens to protect against UV-induced skin damage. Small rutile needles present in gems are responsible for an optical phenomenon known as asterism. Asteriated gems are known as "star" gems. Star sapphires, star rubies, other "star" gems are sought after and are more valuable than their normal counterparts. Rutile is used as a welding electrode covering, it is used as a part of the ZTR index, which classifies weathered sediments. Rutile, as a large band-gap semiconductor, has in recent decades been the subject of significant research towards applications as a functional oxide for applications in photocatalysis and dilute magnetism.
Research efforts utilize small quantities of synthetic rutile rather than mineral-deposit derived materials. Synthetic rutile is sold under a variety of names, it can be produced from the titanium ore ilmenite through the Becher process. Pure synthetic rutile is transparent and colorless, being yellow, in large pieces. Synthetic rutile can be made in a variety of colors by doping; the high refractive index gives an adamantine luster and strong refraction that leads to a diamond-like appearance. The near-colorless diamond substitute is sold as "Titania", the old-fashioned chemical name for this oxide. However, rutile is used in jewellery because it is not hard, measuring only about 6 on the Mohs hardness scale; as the result of growing research interest in the photocatalytic activity of titanium dioxide, in both anatase and rutile phases, rutile TiO2 in powder and thin film form is fabricated in laboratory conditions through solution based routes using inorgainc precursors or organometallic precursors (typically alkoxides such as titanium isopropoxide known as
Triclinic crystal system
In crystallography, the triclinic crystal system is one of the 7 crystal systems. A crystal system is described by three basis vectors. In the triclinic system, the crystal is described by vectors of unequal length, as in the orthorhombic system. In addition, the angles between these vectors must all be different and may include 90°; the triclinic lattice is the least symmetric of the 14 three-dimensional Bravais lattices. It has the minimum symmetry all lattices have: points of inversion at each lattice point and at 7 more points for each lattice point: at the midpoints of the edges and the faces, at the center points, it is the only lattice type. The triclinic crystal system class names, Schönflies notation, Hermann-Mauguin notation, point groups, International Tables for Crystallography space group number, orbifold and space groups are listed in the table below. There are a total 2 space groups. With each only one space group is associated. Pinacoidal is known as triclinic normal. Pedial is triclinic hemihedral Mineral examples include plagioclase, rhodonite, turquoise and amblygonite, all in triclinic normal.
Crystal structure Hurlbut, Cornelius S..
Diaboleite
Diaboleite is a blue-colored mineral with formula Pb2CuCl24. It was discovered in England in 1923 and named diaboleite, from the Greek word διά and boleite, meaning "distinct from boleite"; the mineral has since been found in a number of countries. Diaboleite is pale blue in transmitted light; the mineral occurs as tabular crystals up to 2 cm in size, as subparallel aggregates, or it has massive habit. Vicinal forms of the tabular crystals have a square or octagonal outline and exhibit pyramidal hemihedralism. Diaboleite occurs in manganese oxide ores, as a secondary mineral in lead and copper oxide ores, in seawater-exposed slag. Diaboleite has been found in association with atacamite, caledonite, chloroxiphite, leadhillite, paratacamite and wherryite. A study in 1986 synthesized diaboleite crystals up to 0.18 mm in size using two different methods. The study demonstrated that diaboleite is a low-temperature phase, stable under hydrothermal conditions at temperatures less than 100 to 170 °C. At higher temperatures, the first stable mineral to form is cumengeite.
In 1923, diaboleite was discovered at Higher Pitts Mine in the Mendip Hills of Somerset and described by L. J. Spencer and E. D. Mountain; the study of the similar mineral boleite was perplexing at the time and this new mineral only compounded the difficulty. As insufficient material was available for a full investigation and Mountain named it diaboleite, meaning "distinct from boleite", out of "desperation"; the mineral was grandfathered as a valid mineral by the International Mineralogical Association as it was described prior to 1959. As of 2012, diaboleite has been found in Australia, Chile, Germany, Iran, Russia, South Africa, the UK and the US; the type material is held at the Natural History Museum in London and the National Museum of Natural History in Washington, D. C. Citations BibliographySpencer, L. J.. "Diaboleite". Mineralogical Magazine. Mineralogical Society. 20: 78–80. Doi:10.1180/minmag.1923.020.102.01. Winchell, R. E.. E.. "Synthesis and Study of Diaboleïte". Mineralogical Magazine. Mineralogical Society.
36: 933–939. Doi:10.1180/minmag.1968.283.036.03. Cooper, Mark A.. "Diaboleite, Pb2Cu4Cl2, a defect perovskite structure with stereoactive long-pair behavior of Pb". Canadian Mineralogist. 33: 1125–1129. Palache, Charles. "Diabloeite from Mammoth Mine, Arizona". American Mineralogist. Mineralogical Society of America. 26: 605–612. Media related to Diaboleite at Wikimedia Commons
Tugtupite
Tugtupite is a beryllium aluminium tectosilicate. It contains sodium and chlorine and has the formula Na4AlBeSi4O12Cl. Tugtupite is a member of the silica deficient feldspathoid mineral group, it occurs in high alkali intrusive igneous rocks. Tugtupite is tenebrescent, sharing much of its crystal structure with sodalite, the two minerals are found together in the same sample. Tugtupite occurs as vitreous, transparent to translucent masses of tetragonal crystals and is found in white, pink, to crimson, blue and green, it has a Mohs hardness of 4 and a specific gravity of 2.36. It fluoresces crimson under ultraviolet radiation, it was first found in 1962 at Tugtup agtakôrfia Ilimaussaq intrusive complex of southwest Greenland. It has been found at Mont-Saint-Hilaire in Quebec and in the Lovozero Massif of the Kola Peninsula in Russia The name is derived from the Greenlandic Inuit word for reindeer, means "reindeer blood."The U. S. Geological Survey reports that in Nepal, tugtupite were found extensively in most of the rivers from the Bardia to the Dang.
It is used as a gemstone
Cubic crystal system
In crystallography, the cubic crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most simplest shapes found in crystals and minerals. There are three main varieties of these crystals: Primitive cubic Body-centered cubic, Face-centered cubic Each is subdivided into other variants listed below. Note that although the unit cell in these crystals is conventionally taken to be a cube, the primitive unit cell is not; the three Bravais lattices in the cubic crystal system are: The primitive cubic system consists of one lattice point on each corner of the cube. Each atom at a lattice point is shared between eight adjacent cubes, the unit cell therefore contains in total one atom; the body-centered cubic system has one lattice point in the center of the unit cell in addition to the eight corner points. It has a net total of 2 lattice points per unit cell; the face-centered cubic system has lattice points on the faces of the cube, that each gives one half contribution, in addition to the corner lattice points, giving a total of 4 lattice points per unit cell.
Each sphere in a cF lattice has coordination number 12. Coordination number is the number of nearest neighbours of a central atom in the structure; the face-centered cubic system is related to the hexagonal close packed system, where two systems differ only in the relative placements of their hexagonal layers. The plane of a face-centered cubic system is a hexagonal grid. Attempting to create a C-centered cubic crystal system would result in a simple tetragonal Bravais lattice; the isometric crystal system class names, point groups, examples, International Tables for Crystallography space group number, space groups are listed in the table below. There are a total 36 cubic space groups. Other terms for hexoctahedral are: normal class, ditesseral central class, galena type. A simple cubic unit cell has a single cubic void in the center. A body-centered cubic unit cell has six octahedral voids located at the center of each face of the unit cell, twelve further ones located at the midpoint of each edge of the same cell, for a total of six net octahedral voids.
Additionally, there are 24 tetrahedral voids located in a square spacing around each octahedral void, for a total of twelve net tetrahedral voids. These tetrahedral voids are not local maxima and are not technically voids, but they do appear in multi-atom unit cells. A face-centered cubic unit cell has eight tetrahedral voids located midway between each corner and the center of the unit cell, for a total of eight net tetrahedral voids. Additionally, there are twelve octahedral voids located at the midpoints of the edges of the unit cell as well as one octahedral hole in the center of the cell, for a total of four net octahedral voids. One important characteristic of a crystalline structure is its atomic packing factor; this is calculated by assuming that all the atoms are identical spheres, with a radius large enough that each sphere abuts on the next. The atomic packing factor is the proportion of space filled by these spheres. Assuming one atom per lattice point, in a primitive cubic lattice with cube side length a, the sphere radius would be a⁄2 and the atomic packing factor turns out to be about 0.524.
In a bcc lattice, the atomic packing factor is 0.680, in fcc it is 0.740. The fcc value is the highest theoretically possible value for any lattice, although there are other lattices which achieve the same value, such as hexagonal close packed and one version of tetrahedral bcc; as a rule, since atoms in a solid attract each other, the more packed arrangements of atoms tend to be more common. Accordingly, the primitive cubic structure, with low atomic packing factor, is rare in nature, but is found in polonium; the bcc and fcc, with their higher densities, are both quite common in nature. Examples of bcc include iron, chromium and niobium. Examples of fcc include aluminium, copper and silver. Compounds that consist of more than one element have crystal structures based on a cubic crystal system; some of the more common ones are listed here. The space group of the caesium chloride structure is called Pm3m, or "221"; the Strukturbericht designation is "B2". One structure is the "interpenetrating primitive cubic" structure called the "caesium chloride" structure.
Each of the two atom types forms a separate primitive cubic lattice, with an atom of one type at the center of each cube of the other type. Altogether, the arrangement of atoms is the same as body-centered cubic, but with alternating types of atoms at the different lattice sites. Alternately, one could view this lattice as a simple cubic structure with a secondary atom in its cubic void. In addition to caesium chloride itself, the structure appears in certain other alkali halides when prepared at low temperatures or high pressures; this structure is more to be formed from two elements whose ions are of the same size. The coordination
Cahnite
Cahnite is a brittle white or colorless mineral that has perfect cleavage and is transparent. It forms tetragonal-shaped crystals and it has a hardness of 3 mohs. Cahnite was discovered in the year 1921, it was named Cahnite to honor Lazard Cahn, a mineral collector and dealer. It is found in the Franklin Mine, in Franklin, New Jersey; until the year 2002, when a sample of cahnite was found in Japan, the only known place that cahnite was located. The geological environment that it occurs in is in pegmatites cutting a changed zinc orebody; the chemical formula for cahnite is Ca2B4. It is made up of 26.91% calcium, 3.63% boron, 25.15% arsenic, 1.35% hydrogen, 42.96% oxygen. It has a molecular weight of 297.91 grams. Cahnite is not radioactive. Cahnite is associated with these other minerals: willemite, pyrochroite, hedyphane and baryte
Pyrolusite
Pyrolusite is a mineral consisting of manganese dioxide and is important as an ore of manganese. It is a black, amorphous appearing mineral with a granular, fibrous or columnar structure, sometimes forming reniform crusts, it has a metallic luster, a black or bluish-black streak, soils the fingers. The specific gravity is about 4.8. Its name is from the Greek for fire and to wash, in reference to its use as a way to remove tints from glass. Pyrolusite and romanechite are among the most common manganese minerals. Pyrolusite occurs associated with manganite, hausmannite, chalcophanite and hematite under oxidizing conditions in hydrothermal deposits, it occurs in bogs and results from alteration of manganite. The metal is obtained by reduction of the oxide with sodium, aluminium, or by electrolysis. Pyrolusite is extensively used for the manufacture of spiegeleisen and ferromanganese and of various alloys such as manganese-bronze; as an oxidizing agent it is used in the preparation of chlorine. Natural pyrolusite has been used in batteries, but high-quality batteries require synthetic products.
Pyrolusite is used to prepare disinfectants and for decolorizing glass. When mixed with molten glass it oxidizes the ferrous iron to ferric iron, so discharges the green and brown tints; as a coloring material, it is used in calico dyeing. Black, manganese oxides with a dendritic crystal habit found on fracture or rock surfaces are assumed to be pyrolusite although careful analyses of numerous examples of these dendrites has shown that none of them are in fact pyrolusite. Instead, they are other forms of manganese oxide; some of the most famous early cave paintings in Europe were executed by means of manganese dioxide. Blocks of pyrolusite are found at Neanderthal sites, it may have been kept as a pigment for cave paintings, but it has been suggested that it was powdered and mixed with tinder fungus for lighting fires. Manganese dioxide, in the form of umber, was one of the earliest natural substances used by human ancestors, it was used as a pigment at least from the middle paleolithic. It may have been used by the Neanderthals in fire-making.
The ancient Greeks had a term μάγνης or Μάγνης λίθος meaning stone of the area called Μαγνησία, referring to Magnesia in Thessaly or to areas in Asia Minor with that name. Two minerals are called namely lodestone and pyrolusite; the term μαγνησία was used for manganese dioxide. In the 16th century it was called "manganesum", it was called Alabandicus and Braunstein. The name of the element manganese was derived from "manganesum", whereas "magnesia" came to mean the oxide of a different element, magnesium. Other manganese oxides: Birnessite Psilomelane This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed.. "Pyrolusite". Encyclopædia Britannica. 22. Cambridge University Press. P. 693
