An authigenic mineral or sedimentary rock deposit is one that was generated where it is found or observed. Can be used to characterize metamorphic minerals formed in situ during metamorphism, or to characterize sedimentary minerals formed during sedimentation (ex: by precipitation or recrystallization) instead of being transported from elsewhere by water or wind. Authigenic sedimentation is one of main constituents of deep sea sedimentation. Autigenic clays tend to reduce the pore throats of grains, thus reducing permeability severely. They also decrease the porosity.
