How do coarse-grained igneous rocks form?

Answer 1

Coarse grained rocks are formed by the slow, gradual cooling, solidification, and crystallization of magma within the earths crust/interior due to limitations of air as a result of absence from the atmospheric environment.

additional. On my seacoast, there are some columnar basalts, the column size of which ranges from 600 mm up to 1m in size, depending on the speed of cooling.

Sedimentary rocks need a word. When a river carrying erosion burden enters a depositional regime (plainlands, a lake, or the sea) the coarse sediments will be deposited first, maybe even as conglomerates. Followed by the sands and the finer materials, and eventually the finest silts, which could remain suspended for a long time.

In some of our New Zealand glacial lakes the finest silts remain in suspension without obvious seasonal variation. These eventually settle out however, and if the mineralogy is appropriate, they could eventually form shales or slates.

Thus this process can be a process for separating one mineral from the others.

To all of the above, metamorphism may impose its effects as well.

Answer 2

Coarse grained igneous rocks are of intrusive origin, which means they cooled slowly. Intrusive igneous rocks have fisible mineral crystals and form when magma pushes its way to Earth's surface and cools slowly.

Answer 3

magma that cooled slowly, allowing formation of large crystals.