The blood pressure decreases and complaints, such as fatigue and lassitude, make themselves felt. These symptoms may also occur after the meal because the blood gathers in the area of the digestive organs and is missing in the brain. Dizziness.
Non-foliated metamorphic rocks such as hornfels, marble, quartzite, and novaculite do not have a layered or banded appearance. Pictures and brief descriptions of some common types of metamorphic rocks are shown on this page. Hornfels is a fine-grained nonfoliated metamorphic rock with no specific composition.
Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means change in form. The original rock (protolith) is subjected to heat (temperatures greater than 150 to 200 Â°C) and pressure (150 megapascals (1,500 bar)), causing profound physical and/or chemical change. The protolith may be a sedimentary, an igneous, or even an existing type of metamorphic rock. Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's current land surface. They are classified by texture and by chemical and mineral assemblage (metamorphic facies).