Feldspathoid · Pseudocubic
Leucite in thin section
Euhedral, pseudocubic crystals with nearly zero birefringence (about 0.001), so nearly black in XPL, with common repeated twinning.
Plane-polarized light
| Color | Colorless |
|---|---|
| Pleochroism (color change on rotation) | None |
| Relief | Low, Negative (below the mount) |
| Cleavage | None |
| Shape | Euhedral |
Cross-polarized light
| Maximum birefringence | about 0.001 |
|---|---|
| Highest interference color | Black at all angles, 1st-order gray–white |
| Twinning | Polysynthetic stripes, Sector / wedge |
Telling it apart
Analcime looks similar. Garnet has high relief.
Where you'll find it
Potassic volcanic rocks
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