... polarized light, 40x NNH-3 Actinolite in a greenstone Like most monoclinic amphiboles actinolite has birefringence in the lower 2nd order Twinning, possibly relic from the original augite, can be seen ... Cummingtonite in a hornblende - biotite - cummingtonite amphibolite Like most monoclinic amphiboles, birefringence is in the lower second order Cross polarized light, 100x Q-603C Cummingtonite in ... pleochroic chlorite This grain has prominent twinning, evident in parallel stripes having somewhat different pleochroic colors Plane polarized light, 20x IMA96-C1-1 Chloritoid in a muscovite-chlorite...