Oxides / sulfides · Opaque
Opaque minerals in thin section
Black in both PPL and XPL. Identifying them (magnetite, ilmenite, pyrite and others) requires reflected light.
Plane-polarized light
| Color | Opaque (black) |
|---|---|
| Pleochroism (color change on rotation) | None |
| Cleavage | None |
| Shape | Euhedral, Anhedral / equant |
Cross-polarized light
| Maximum birefringence | about 0.000 |
|---|---|
| Highest interference color | opq, Black at all angles |
| Twinning | None |
Telling it apart
Use reflected light to tell opaque minerals apart.
Where you'll find it
Nearly every rock
Photo examples
Photos open on the source sites.
Identify an unknown grain Read interference colors Practice mineral ID
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