|
Rutile
|
|
Property
|
Value
|
Comments
|
| Formula |
TiO2
|
Commonly pure TiO2 ; Subsitution for Ti may include Fe, Ta, Sn, Nb ; possible presence of Cr and V
|
| Crystal System |
Tetragonal |
|
| Crystal Habit |
Prisms, contact twins (elbow or cyclic-shaped){101} |
"needle-like" crystals in thin section |
| Birefringence |
0.286-0.296 |
Extreme/distinct but often masked by rich mineral color, intense birefringence makes determining sign of elongation impractical
|
| Cleavage |
{110}good, {100} moderate: parting on {092} and {011} |
Barely visible in thin section |
Optic Sign
|
Uniaxial (+)
|
| Hardness |
6-6.5 |
| Specific Gravity |
4.23-5.5 |
| Color/Pleochroism |
Reddish-brown; yellow-brown; interference figures can have numerous isochromes; weak pleochroism
|
Refractive Index
|
Omega: 2.605-2.613
Epsilon: 2.899-2.901
|
| Distinguishing Features |
Thin section characterized by very high relief and extreme birefringence; rich yellowish-reddish brown color with depth of color relating to ferric iron, niobium, and tantalum content |
| Occurrence |
Fairly widespread accessory mineral in metamorphic rocks and as larger crystals in pegmatites; fine rutile needle inclusions fairly common in transparent quartz, intergrowths found with ilmenite |
| Editors |
Hillary Friedman ('08), Emily DeWitt ('19) |
