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.
A metamorphic rock used to be some other type of rock, but it was changed inside the Earth to become a new type of rock. The word metamorphism comes from ancient Greek words for change (meta) and form (morph). The type of rock that a metamorphic rock used to be, prior to metamorphism, is called the protolith. During metamorphism the mineral content and texture of the protolith are changed due to changes in the physical and chemical environment of the rock. Metamorphism can be caused by burial, tectonic stress, heating by magma, or alteration by fluids. At advanced stages of metamorphism, it is common for a metamorphic rock to develop such a different set of minerals and such a thoroughly changed texture that it is difficult to recognize what the protolith was.