Wine-red rutile crystals from Binn Valley, Switzerland (Size: 2.0 x 1.6 x 0.8 cm)
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Name | Rutile |
Category | Oxide minerals |
Caption | Wine-red rutile crystals from Binn Valley, Switzerland (Size: 2.0 x 1.6 x 0.8 cm) |
Formula | TiO2 |
Strunz | 04.DB.05 |
Symmetry | Tetragonal 4/m 2/m 2/m; space group 136 |
Unit Cell | a=4.5937 Å, c=2.9587 Å; Z=2 |
Color | Reddish brown, red, pale yellow, pale blue, violet, rarely grass-green; black if high in Nb � Ta |
Habit | Acicular to Prismatic crystals, elongated and
striated parallel to [001] |
System | Tetragonal ditetragonal dipyramidal |
Twinning | Comon on {011}, or {031}; as contact twins with two, six, or eight individuals, cyclic, polysynthetic |
Cleavage | {110} good, 100 moderate, parting on {092} and {011} |
Fracture | Uneven to sub-conchoidal |
Mohs | 6.0 - 6.5 |
Luster | Adamantine to submetallic |
Refractive | nω=2.605 � 2.613 �nε=2.899 � 2.901 |
Opticalprop | Uniaxial (+) |
Birefringence | 0.2870-0.2940 |
Pleochroism | Weak to distinct brownish red-green-yellow |
Dispersion | strong |
Anisotropism | strong |
Streak | Bright red to dark red |
Gravity | 4.23 increasing with Nb � Ta content |
Fusibility | Fusible in alkali carbonates |
Solubility | Insoluble in acids |
Diaphaneity | Opaque, transparent in thin fragments |
Impurities | Fe, Nb, Ta |
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Rutile is a mineral composed primarily of titanium dioxide, TiO2.
Rutile is the most common natural form of TiO2. Two rarer polymorphs of TiO2 are known:
*anatase (sometimes known by the obsolete name 'octahedrite'), a tetragonal mineral of pseudo-octahedral habit; and
*brookite, an orthorhombic mineral.
Rutile has among the highest refractive indices of any known mineral and also exhibits high dispersion. Natural rutile may contain up to 10% iron and 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.
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