What is the primary component of argillite/slate?

The primary component of argillite, also known as slate when it undergoes further metamorphism, is indeed the metamorphic equivalents of siltstone or shale. Argillite forms from the compaction and cementation of fine-grained sediment, typically consisting of clay and silt particles. As these sediments are subjected to increased pressure and temperature over geological time, they metamorphose to form argillite.

When discussing slate specifically, it is important to note that it represents a more advanced stage in the metamorphic process of argillite. The transformation involves the alignment of platy minerals, making Slate distinct in its properties, such as its ability to split into thin, flat sheets. This process highlights the relationship between the original sedimentary rocks (siltstone and shale) and their metamorphic counterparts, illustrating how they are fundamentally linked in the rock cycle.

The other options do not represent the primary components or formations of argillite/slate. For instance, granite is an igneous rock, unrelated to the sedimentary origins of argillite. Similarly, igneous rock does not pertain to the metamorphic processes that transform siltstone and shale into argillite. Lastly, light-colored sandstone, being a sediment