Anatase rutile TiO2 crystal.
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Anatase is a metastable mineral form of titanium dioxide. The mineral in natural forms is mostly encountered as a black solid, although the pure material is colorless or white. Two other naturally occurring mineral forms of TiO2 are known, brookite and rutile.
The stone is always found as small, isolated and sharply developed crystals, and like the thermodynamically stable rutile, it crystallizes in the tetragonal system.
The gemstone is metastable at all temperatures and pressures, with rutile being the equilibrium polymorph. Nevertheless, The stone 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.
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 pyramid, 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’. Due to this steeper pyramid,
Two growth habits of anatase TiO2 crystals may be distinguished. The more common occurs as simple acute double pyramids with an indigo-blue to black color and steely luster. 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. The plane is the most thermodynamically stable surface and is thus the most widely exposed facet in natural and synthetic stone.
Crystals of the second type have numerous pyramidal faces developed, and they are usually flatter or sometimes prismatic in habit, the color 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. Naturally occurring pseudomorphs of rutile after anatase TiO2 crystal are also known.
Anatase meaning and healing properties benefits
The following section is pseudo scientific and based on cultural beliefs.
The stone helps us to view problems from all angles, thereby making it easier to find a clear and decisive solution. In healing, it can be used to treat sinus problems, but otherwise is useful mainly on a mental and spiritual level.
Anatase under microscope
Where is anatase mineral found?
It is found as hard, brilliant crystals of tetragonal symmetry and various colors in veins in igneous and metamorphic rocks and commonly in placer deposits of detritus. Notable vein deposits exist in many regions of the Alps; placer deposits are common in Minas Gerais and Bahia, Brazil.
What is difference between anatase crystal and rutile?
Rutile is deep red while the stone is yellow to blue. Rutile has a high absorbance property. They are both used in the white pigmentation of paints, paper, and ceramics.
Why is anatase a better photocatalyst than rutile?
The activity increases for films up to 5 nm thick, while rutile films reach their maximum activity for 2.5 nm films already. This shows that charge carriers excited deeper in the bulk contribute to surface reactions in anatase than in rutile.
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