What is the raw materials of metamorphic rocks?

Well, what does metamorphosis mean?

So changed from some other rock, for example from sandstone or limestone by heat and pressure.
https://www.merriam-webster.com/dictionary/metamorphosis

To determine the raw materials of metamorphic rocks, we need to understand the process of metamorphism. Metamorphism is the transformation of existing rocks into new rocks due to intense heat, pressure, or chemical activity within the Earth's crust. It involves changes in the mineral composition, texture, and structure of the parent rocks, which are also known as protoliths.

The raw materials of metamorphic rocks can vary depending on the type of protolith involved. Protoliths are the initial rocks that undergo metamorphism. They can be sedimentary, igneous, or even other metamorphic rocks. The composition of the protolith determines the mineral content of the resulting metamorphic rock.

For example, if the protolith is a sedimentary rock composed mainly of clay minerals, such as shale, the resulting metamorphic rock would likely contain minerals like muscovite, biotite, and chlorite. On the other hand, if the protolith is an igneous rock rich in minerals like quartz and feldspar, such as granite, the metamorphic rock may consist of minerals like quartz, feldspar, and mica.

In general, metamorphic rocks can contain a wide range of minerals, including quartz, feldspar, mica, amphibole, garnet, and many others. The specific minerals present depend on factors such as the temperature, pressure, and presence of fluids during the metamorphic process.

To determine the raw materials of a specific metamorphic rock, you would need to identify the type of protolith and the resulting mineral composition through laboratory analysis, microscopic examination, or studying the rock's physical properties.