what are the properties and characteristics of metamorphic rock
The correct answer and explanation is:
Metamorphic rocks are types of rocks that have undergone a transformation due to intense heat, pressure, or chemically active fluids. This process, called metamorphism, alters the mineral composition and structure of pre-existing rocks, which can be igneous, sedimentary, or even other metamorphic rocks.
One key property of metamorphic rocks is their foliation. Foliation refers to the repetitive layering or banding seen in many metamorphic rocks, caused by the reorientation of minerals under directed pressure. Examples include slate, schist, and gneiss, where minerals align to form distinct layers or bands. However, not all metamorphic rocks exhibit foliation. Non-foliated metamorphic rocks like marble and quartzite lack this layered texture because their mineral grains recrystallize without a preferred orientation.
Another important characteristic is increased density and hardness compared to their original rocks. Due to recrystallization under heat and pressure, minerals in metamorphic rocks often grow larger and become more tightly packed, making the rock more compact and harder. This change affects the rock’s durability and resistance to weathering.
Metamorphic rocks also display new mineral formation. During metamorphism, minerals that are stable under high pressure and temperature form, such as garnet, kyanite, and staurolite. These new minerals are indicators of the metamorphic conditions the rock has experienced.
The texture of metamorphic rocks varies widely. Besides foliation, textures can be granular or porphyroblastic, where larger crystals, called porphyroblasts, grow within a finer-grained matrix. The grain size often increases with the grade of metamorphism, meaning rocks formed under higher temperature and pressure usually have coarser textures.
Lastly, metamorphic rocks can retain some features of their original rock, known as protolith, but their mineral and structural characteristics reflect the conditions of metamorphism. Overall, metamorphic rocks are significant for understanding the dynamic processes inside the Earth and often form important geological resources like building stones and gemstones.