Black, reddish to yellowish brown, dark blue, gray
Crystal habit
Pyramidal (crystals are shaped like pyramids), tabular (form dimensions are thin in one direction).
Twinning
Rare on {112}
Cleavage
Perfect on [001] and [011]
Fracture
Subconchoidal
Tenacity
Brittle
Mohs scale hardness
5.5–6
Luster
Adamantine to splendent, metallic
Streak
Pale yellowish white
Diaphaneity
Transparent to nearly opaque
Specific gravity
3.79–3.97
Optical properties
Uniaxial (−), anomalously biaxial in deeply colored crystals
Refractive index
nω = 2.561, nε = 2.488
Birefringence
δ = 0.073
Pleochroism
Weak
References
[2][3][4]
Anatase is a metastable mineral form of titanium dioxide (TiO2) with a tetragonal crystal structure. Although colorless or white when pure, anatase in nature is usually a black solid due to impurities. Three other polymorphs (or mineral forms) of titanium dioxide are known to occur naturally: brookite, akaogiite, and rutile, with rutile being the most common and most stable of the bunch. Anatase is formed at relatively low temperatures and found in minor concentrations in igneous and metamorphic rocks.[5] Glass coated with a thin film of TiO2 shows antifogging and self-cleaning properties under ultraviolet radiation.[6]
Anatase is always found as small, isolated, and sharply developed crystals, and like rutile, it crystallizes in a tetragonal system. Anatase is metastable at all temperatures and pressures, with rutile being the equilibrium polymorph. Nevertheless, anatase is often the first titanium dioxide phase to form in many processes due to its lower surface energy, with a transformation to rutile taking place at elevated temperatures.[7] Although the degree of symmetry is the same for both anatase and rutile phases, there is no relation between the interfacial angles of the two minerals, except in the prism-zone of 45° and 90°. The common octahedral crystal habit of anatase, with four perfect cleavage planes, has an angle over its polar edge of 82°9', whereas rutile octahedra only has a polar edge angle of 56°52½'. The steeper angle gives anatase crystals a longer vertical axis and skinnier appearance than rutile, which led French mineralogist René Just Haüy to name the mineral anatase in 1801, from the Greek anatasis ("extension"). Additional important differences exist between the physical characters of anatase and rutile. For example, anatase is less hard (5.5–6 vs. 6–6.5 on the Mohs scale) and less dense (specific gravity about 3.9 vs. 4.2) than rutile. Anatase is also optically negative, whereas rutile is optically positive. Anatase has a more strongly adamantine or metallic-adamantine luster than that of rutile as well.[8]
^Hanaor, Dorian A. H.; Sorrell, Charles C. (2011). "Review of the anatase to rutile phase transformation". Journal of Materials Science. 46 (4): 855–874. Bibcode:2011JMatS..46..855H. doi:10.1007/s10853-010-5113-0. S2CID 97190202.
^One or more of the preceding sentences incorporates text from a publication now in the public domain: Spencer, Leonard James (1911). "Anatase". In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 1 (11th ed.). Cambridge University Press. pp. 919–920.
Anatase is a metastable mineral form of titanium dioxide (TiO2) with a tetragonal crystal structure. Although colorless or white when pure, anatase in...
bonded to three Ti centers. The overall crystal structures of rutile and anatase are tetragonal in symmetry whereas brookite is orthorhombic. The oxygen...
forms are akaogiite (monoclinic), anatase (tetragonal) and rutile (tetragonal). Brookite is rare compared to anatase and rutile and, like these forms,...
common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest refractive indices...
varies in color from yellow to brown. It consists mainly of rutile or anatase. It is observed in some igneous rocks and iron ore deposits as the result...
experiments which produced anatase at an early stage of a medieval iron-gall ink production process. Examination of her anatase by a colleague, mineralogist...
Nanosized particles of titanium dioxide tend to form in the metastable anatase phase, due to the lower surface energy of this phase, relative to the equilibrium...
soils is approximately 0.5–1.5%. Common titanium-containing minerals are anatase, brookite, ilmenite, perovskite, rutile, and titanite (sphene). Akaogiite...
aluminium clay mineral kaolinite (Al2Si2O5(OH)4) and small amounts of anatase (TiO2) and ilmenite (FeTiO3 or FeO·TiO2). Bauxite appears dull in luster...
Bibcode:2015CaJPh..93..974L. doi:10.1139/cjp-2014-0518. S2CID 54966950. Anatase to Rutile Transition ART, in J. Mat. Sci. Molodets, A. M.; Nabatov, S....
are common in condensed matter and crystallography. This is the case for anatase, a metastable polymorph of titanium dioxide, which despite commonly being...
that may rely on structural features such as phase hetero-junctions (e.g. anatase-rutile interfaces), noble-metal nanoparticles, silicon nanowires and substitutional...
1921. It is made out of titanium dioxide, from the minerals brookite, anatase, rutile, or ilmenite, currently the major source. Because of its brilliant...
coke; heat treatment to effect phase transformations, as in conversion of anatase to rutile or devitrification of glass materials; removal of ammonium ions...
rutile and anatase), ferromagnetic above 400 K Chromium-doped rutile, ferromagnetic above 400 K Iron-doped rutile and iron-doped anatase, ferromagnetic...
indium tin oxide (ITO), fluorine doped tin oxide (FTO), niobium doped anatase TiO2 (NTO) or doped zinc oxide. Organic films are being developed using...
titanium dioxide (TiO2). It is a high-pressure polymorph of TiO2, along with anatase, brookite and another high-pressure phase called "TiO2 II". Rutile is the...
between cells Titanium nanotubes, created by the conversion of the mineral anatase by hydrothermal synthesis Chiraltube. Atomistic builder for any nanotubes...
plastics. It has very high refraction index (rutile modification 2.7 and anatase modification 2.55) and optimum refraction is obtained with crystals about...
varying factors such as temperature, such as in the transformation of anatase to rutile phases of titanium dioxide. There are many examples of natural...
the lustre (sheen) of synthetic fibres. The most common delustrant is anatase titanium dioxide. Synthetic fibres such as nylon are normally extremely...