Which of the following is not a metamorphic rock?

Loess is not a metamorphic rock. Metamorphic rocks are formed from the transformation of existing rocks through heat, pressure, and chemical processes. Slate, marble, and gneiss are all examples of metamorphic rocks. Slate is formed from the metamorphism of shale or mudstone, marble from the metamorphism of limestone, and gneiss from the metamorphism of other rocks such as granite or schist. In contrast, loess is a type of sediment that is made up of fine-grained, windblown particles such as silt, sand, and clay. It is deposited in areas such as floodplains and desert basins and can be several meters thick. In summary, loess is not a metamorphic rock, while slate, marble, and gneiss are all examples of metamorphic rocks. Loess is a type of sediment that is deposited in areas such as floodplains and desert basins.