https://www.usgs.gov/media/images/hydrothermal-alteration-makes-lava-creek-tuff-appear-different
hydrothermal alteration makes Lava Creek Tuff appear different | U.S. Geological Survey
Example of how the same rock type can look very different due to hydrothermal alteration. Left image is of the Lava Creek Tuff, which erupted during the...
lava creek tuffhydrothermal alteration