Propylite is a hydrothermally altered andesite that resembles a greenstone.
It typically contains secondary minerals such as calcite, chlorite, epidote, serpentine, quartz, pyrite, and iron oxides.
This rock forms as a low- to medium-temperature metasomatic product (chemical alteration by fluids) of basic to intermediate volcanic rocks, particularly around hydrothermal ore deposits or during magmatic alteration processes.
