This chapter discusses mineralogy and petrology of burial diagenesis and incipent metamorphism in clastic rocks. The phase-modification processes referred to as “late-diagenetic” or “epigenetic” (or catagenetic) are metamorphic in nature. Hence, the distinction between burial diagenesis and lowest-grade regional metamorphism is largely artificial and arbitrary. The modification of various kinds of sedimentary rocks upon burial has largely been studied by investigators from different sub-disciplines within the earth sciences: (1) changes in mineralogy of clay-rich sedimentary rocks by sedimentary petrographers and clay mineralogists; (2) authigenic mineral assemblages in tuffs and volcanic sediments by metamorphic petrologists; and (3) changes in the constitution of coaly and other organic matter by coal petrologists, and organic geochemists. The growing awareness of the overlap in space of the physical conditions and of the chemical influences controlling these phenomena warrants renewed efforts to correlate the changes in various types of sedimentary rocks in order to arrive, ultimately, at an integrated picture of the phase changes in different types of sedimentary rocks upon burial and incipient metamorphism. This chapter intends to contribute to such an integrated picture.