Formation
(1) Metamorphic through the transformation of magnesium-rich minerals (such as olivine, pyroxene, or biotite) under low- to medium-grade conditions of the green schist facies.
(2) Hydrothermal as an alteration product of mafic rocks and in alpine fissure fillings through precipitation from magnesium-rich aqueous solutions.
(3) Metasomatic in contact zones between silica-rich and magnesium-rich rocks (e.g. chlorite schist formation).
