Formation
(1) Hydrothermal, formed by precipitation from low-temperature aqueous solutions in cavities within igneous rocks, primarily as a late-stage crystallization product in basaltic lava.
(2) Metamorphic, formed during low-grade regional metamorphism in the zeolite facies at temperatures below 250 °C.
(3) As a result of alpine fracturing (secondary) due to hydrothermal mobilization in metamorphic rocks such as gneisses or amphibolites
