Ok this is a science question If you know metamorphic rocks come here!?

Question

Why are metamorphic rocks formed by contact metamorphism usually not as denseas those formed by regional matemorphism?

How could you diferentiate between white marble and white quartzite?

Why do minerals in metamorphic rocks often rearrange in layers?

Why is quartzite very hard and more resistant than its parent rock?

On what basis can metamorphic rocks be identified?

Answer 1

Compactness of rocks - the statement is not true. Contact metamorphism can produce compact rocks. Since contact metamorphism is produced in the country rock in contact with a magma, the rise in temperature for a short time plays the all important role and since it is of very limited extent, pressure is nearly constant. The first factor makes the rock fine grained and the second factor (i.e., lack of stress) makes the rock equigranular. Since no cleavage / foliation / banding is generally produced, the rock remains compact.

Simply by identifying the mineral composition - it is not at all difficult to distinguish a carbonate mineral, like calcite, from a quartz. Moreover there is acid test.

Due to preferred orientation of phyllosilicates or flaky minerals. The rock when subjected to pressure, the flaky minerals get rearranged to form a metamorphic differentiation banding, with or without recrystallisation.

Because it undergoes a chemical change. The sandy sediments are lithified due to overburden pressure to form sandstone. The intergranular spaces are filled up by matrix and cementing material (generally ferruginous or siliceous). This, when suffer metamorphism, undergoes a chemical change due to action of pressure, temperature and chemically active fluid. So at the end the grains get well-knit.

Generally on the basis of metamorphic minerals, particularly metamorphic Index minerals. Also by the texture.

Answer 2

Google it. Your question is compound, split it up.