Nesosilicate · Biaxial (±)
Olivine in thin section
Colorless to pale yellow (darker with more iron), high relief, high birefringence (about 0.033–0.042). Recognized by its distinctive irregular fractures, lack of cleavage and its alteration products.
Plane-polarized light
| Color | Colorless, Yellow |
|---|---|
| Pleochroism (color change on rotation) | None |
| Relief | High |
| Cleavage | None |
| Shape | Anhedral / equant, Euhedral |
Cross-polarized light
| Maximum birefringence | about 0.038 |
|---|---|
| Highest interference color | 2nd-order blues, greens, 3rd-order |
| Extinction | Parallel |
| Twinning | None |
Telling it apart
Clinopyroxenes have somewhat lower birefringence and recognizable cleavage.
Where you'll find it
Basalt, gabbro, peridotite, dunite
Photo examples
Alex Strekeisen · Search Wikimedia Commons
Photos open on the source sites.
Identify an unknown grain Read interference colors Practice mineral ID
Related minerals
Sources
OpticMin, ATHENA, Univ. of Geneva (P. Perroud) · Alex Strekeisen thin-section collection · Distinguishing features of minerals (UT Arlington) · MIT OCW 12.109 amphibole lab · SEPM Strata: carbonate staining · Wikipedia mineral pages (infobox optical data) · Athabasca University rocks and minerals · Smith College petrography: perthite