 |
Photomicrograph of anahedral grains in plane polarized light. From a Blue Shist, Cyros, Greese. (JBB-99-15E) Click on the thumbnail to see a larger ppl/xpl rollover image. |
|
|
||
|
|
|
|
| Formula | TiO2 |
Commonly pure TiO2 ; Subsitution for Ti may include Fe, Ta, Sn, Nb ; possible presence of Cr and V |
| Crystal System | Tetrahedral | |
| Crystal Habit | Prisms, Contact Twins (elbow or cyclic-shaped){101} | "needle-like" cyrstals in thin section |
| Birefringence | 0.29 | Extreme/distinct but often masked by rich mineral color ; intense birefringence makes determining sign of elongation impractical |
| Cleavage | {110} and{010} | 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 (Omega > Epsilon) |
|
| Refractive Index
|
Omega: 2.605-2.613 |
|
| Distinguishing Features | Extreme positive relief in thin section; rich yellowish-reddish brown color in thin section | |
| Occurrence | Very stable in weathering envirnments, common in clastic sediments; Fine fibers found as inclusions in quartz; Large crystals found in Pegmatites; Placer deposits for Titanium | |
| Editors | Hillary Friedman ('08) | |
|
Photomicrograph of anahedral grains in plane polarized light. From a Blue Shist, Cyros, Greese. (JBB-99-15E) Click on the thumbnail to see a larger ppl/xpl rollover image. |