Phyllosilicate · Biaxial (−)
Serpentine in thin section
Colorless to pale green with low 1st-order gray colors (antigorite birefringence about 0.005–0.006). Commonly forms a mesh texture where it replaces olivine; cross-fiber chrysotile occurs in veins. The varieties are hard to tell apart without X-ray diffraction.
Plane-polarized light
| Color | Colorless, Green |
|---|---|
| Pleochroism (color change on rotation) | None, Weak |
| Relief | Low |
| Cleavage | None |
| Shape | Needles / fibrous |
Cross-polarized light
| Maximum birefringence | about 0.006 |
|---|---|
| Highest interference color | 1st-order gray–white |
| Extinction | Parallel |
| Twinning | None |
Telling it apart
Chlorite is more strongly pleochroic. Fibrous amphiboles have higher indices and birefringence.
Where you'll find it
Serpentinite, altered peridotite
Photo examples
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