Interaction of polarised light with minerals:LAB TS-1:Double refractionReliefColour and pleochroismOther properties that can be observed in PPLLAB TS-2:Isotropy and anisotropyBirefringence and interferenceExtinction angleSign of elongation. Nesse, 2000; Fig. 7.4. Polarisation. unpolarised light(all possible vibration directions).