Types of rocks

There are three major groups of rocks and it is quite easy to distinguish their differences.
Igneous rocks are those that have formed by the cooling and crystallization of magma, either at the Earth’s surface or within the crust.
Sedimentary rocks are those that have formed when eroded particles of other rocks have been deposited (on the ocean floor, streams/lake beds, etc.) and compacted, or by the precipitation of minerals from water.
Metamorphic rocks are those that have formed when existing rocks have undergone pressure and / or temperature changes so that their original mineralogy has been changed. Each of these rock groups contains many different types of rock, and each can be identified from its physical features. Being able to describe and name rocks is one of the fundamental skills of a geologist. Important information regarding the nature of rocks is communicated through concise, accurate descriptions. This information allows the geologist to identify the rock, and, in the process, to learn about its history and the geological environment in which it was formed.

Question: