Three crystals from Gouveia, Minas Gerais, Brazil Anatase is one of the three mineral forms of titanium dioxide (the other two being brookite and rutile). It is always found as small, isolated and sharply developed crystals, and like rutile, a more commonly occurring modification of titanium dioxide, it crystallizes in the tetragonal system; but, although the degree of symmetry is the same for both, there is no relation between the interfacial angles of the two minerals, except, of course, in the prism-zone of 45° and 90°. The common pyramid of anatase, parallel to the faces of which there are perfect cleavages, has an angle over the polar edge of 82°9', the corresponding angle of rutile being 56°52½'It was on account of this steeper pyramid of anatase that the mineral was named, by RJ Haüy in 1801, from the Greek anatasis, "extension," the vertical axis of the crystals being longer than in rutile. There are also important differences between the physical characters of anatase and rutile; the former is not quite so hard (H=5½-6) or dense (specific gravity 3.9); it is optically negative, rutile being positive; and its lustre is even more strongly adamantine or metallic-adamantine than that of rutile. Image File history File links Download high-resolution version (1179x882, 647 KB) Anatase(TiO2) crystals Origin: Gouveia, MG, Brazil Description: Brown color crystals (~2 x 1cm) Source: The authors are owners Date: created 2005-12-07 Authors: Tom Epaminondas (mineral collector) / Eurico Zimbres (FGEL-UERJ) Permission = Free for all use...
Image File history File links Download high-resolution version (1179x882, 647 KB) Anatase(TiO2) crystals Origin: Gouveia, MG, Brazil Description: Brown color crystals (~2 x 1cm) Source: The authors are owners Date: created 2005-12-07 Authors: Tom Epaminondas (mineral collector) / Eurico Zimbres (FGEL-UERJ) Permission = Free for all use...
Minerals are natural compounds formed through geological processes. ...
Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurring oxide of titanium, chemical formula TiO2. ...
Brookite is a mineral consisting of titanium oxide, TiO2, and hence identical with rutile and anatase in composition, but crystallizing in the orthorhombic system (see crystal structure). ...
Rutile in trellis texture characteristic of secondary rutile. ...
Quartz crystal In chemistry and mineralogy, a crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ...
In crystallography, the tetragonal crystal system is one of the 7 lattice point groups. ...
René Just Haüy (February 28, 1743 – June 3, 1822), French mineralogist, commonly styled the Abbé Haüy, from being an honorary canon of Notre Dame, was born at St Just, in the départment of Oise. ...
The Union Jack, flag of the newly formed United Kingdom of Great Britain and Ireland. ...
Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. ...
Relative density (also known as specific gravity) is a measure of the density of a material. ...
Adamantine is a mineral, often referred to as adamantine spar. ...
Two types or habits of anatase crystals may be distinguished. The commoner occurs as simple acute double pyramids with an indigo-blue to black colour and steely lustre. Crystals of this kind are abundant at Le Bourg-d'Oisans in Dauphiné, where they are associated with rock-crystal, feldspar, and axinite in crevices in granite and mica-schist. Similar crystals, but of microscopic size, are widely distributed in sedimentary rocks, such as sandstones, clays, and slates, from which they may be separated by washing away the lighter constituents of the powdered rock. In mineralogy, shape and size give rise to descriptive terms applied to the typical appearance, or habit of crystals. ...
Le Bourg-dOisans is a town and commune in the Isère département, in south-eastern France. ...
Flag of the Dauphiné Dauphiné is a former province in southeastern France, roughly corresponding to the present départements of the Isère, Drôme, and Hautes-Alpes. ...
Feldspar is the name of an important group of rock-forming minerals which make up perhaps as much as 60% of the Earths crust. ...
Axinite is a brown to violet-brown, or reddish-brown bladed mineral composed of calcium aluminum boro-silicate, (Ca,Fe,Mn)3Al2BO3Si4O12OH. Axinite is pyroelectric and piezoelectric. ...
Quarrying granite for the Mormon Temple, Utah Territory. ...
Rock with mica Mica sheet Mica flakes The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. ...
Schist The schists form a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. ...
Two types of sedimentary rock: limey shale overlaid by limestone. ...
Red sandstone interior of Lower Antelope Canyon, Arizona, worn smooth due to erosion by flash flooding over millions of years Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock grains. ...
The Gay Head cliffs in Marthas Vineyard are made almost entirely of clay. ...
Slate Slate is a fine-grained, homogeneous, metamorphic rock derived from an original sedimentary rock composed of clay or volcanic ash through low grade regional metamorphism. ...
Crystals of the second type have numerous pyramidal faces developed, and they are usually flatter or sometimes prismatic in habit; the colour is honey-yellow to brown. Such crystals closely resemble xenotime in appearance and, indeed, were for a long time supposed to belong to this species, the special name wiserine being applied to them. They occur attached to the walls of crevices in the gneisses of the Alps, the Binnenthal near Brig in canton Valais, Switzerland, being a well-known locality. Xenotime (from the Greek words xenos, foreign, and time, honour) is a rare yttrium phosphate mineral whose chemical formula is YPO4. ...
Gneiss Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from preexisting formations that were originally either igneous or sedimentary rocks. ...
The West face of the Petit Dru above the Chamonix valley near the Mer de Glace. ...
Brig (in French Brigue) is a city in the canton of Valais, Switzerland at 46°19′ N 7°58′ E. The historic town with 5000 inhabitants is part of the municipality Brig-Glis with a 11600 inhabitants. ...
The Valais (German: ) is one of the 26 cantons of Switzerland in the south-western part of the country, in the Pennine Alps around the valley of the Rhone River from its springs to Lake Geneva. ...
When strongly heated, anatase is converted into rutile, changing in specific gravity to 4.1; naturally occurring pseudomorphs of rutile after anatase are also known. Crystals of anatase have and continue to be artificially prepared in laboratories by introducing the moisture-sensitive titanium tetrachloride, TiCl4, to water at very cold temperatures (the process is very exothermic) to produce TiO2 and HCl gas. Such synthetic forms of anatase are currently under scrutiny in the field of semiconductors and photovoltaic materials. Titanium tetrachloride (or titanium(IV) chloride) is the chemical compound with the formla TiCl4. ...
Exothermic means to release energy in the form of heat. ...
A semiconductor is a solid whose electrical conductivity can be controlled over a wide range, either permanently or dynamically. ...
A solar cell, a form of photovoltaic cell, is a device that uses the photoelectric effect to generate electricity from light, thus generating solar power (energy). ...
Another name commonly in use for this mineral is octahedrite, a name which, indeed, is earlier than anatase, and given because of the common (acute) octahedral habit of the crystals. Other names, now obsolete, are oisanite and dauphinite, from the well-known French locality.
References
- This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.
Encyclopædia Britannica, the 11th edition The Encyclopædia Britannica Eleventh Edition (1910–1911) is perhaps the most famous edition of the Encyclopædia Britannica. ...
The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ...
See also |
Feeds |
Contact