A rock or a rock is a solid material from the earth’s crust, which consists of one or more minerals that are linked together. In geology, rock is a natural and solid aggregate of mineral or quasi-mineral materials. The solid outer layer of the earth (lithosphere) is made of rock. There are three types of rocks: igneous, sedimentary and metamorphic. The science of knowing rocks is called petrology. The main component of all rocks is silica.

Stones and minerals are used in construction, industry, medicine, etc. Large pieces of rock that are seen outside the soil are called boulders or rocks.

The major part of the earth’s crust consists of hard rock. Every step of our feet is hard rock. The stone may be covered with a layer of soil. It may be covered by several meters or even several kilometers from a layer of it. But wherever we break the ground enough, we will reach hard rock.[1]

The most important difference between soil and stone is the difference in their compression and adhesion to each other. From the point of view of geology, rock refers to materials from the earth’s crust that are made of one or more minerals that are linked together. On the other hand, soil is a mass of particles with separate or loosely connected grains, which is formed due to the weathering of rocks. However, in engineering and construction works, the drilling ability of geological materials is used as an index in their classification into two groups of rock and soil [2].

stone cycle

Stone cycle diagram. Guide:
1 = magma;
2 = crystallization (stone freezing);
3 = igneous rock;
4 = erosion;
5 = sedimentation;
6 = sediments and sedimentary rocks;
7 = tectonic burial and metamorphism;
8 = transformation stone;
9 = melting.
The rock cycle is a set of processes that lead to the creation of all types of rocks on the earth’s crust and also their transformation into each other. In other words, it is called the set of changes in the size and composition of rocks as a result of various processes such as weathering and solidification of molten materials and the transformation of the rock cycle.

During long periods of time, rocks are crushed due to erosion and after transporting sediments, they finally make sedimentary rock. Sedimentary rock may turn into metamorphic rock due to heat and pressure in the depths of the earth, or it may turn into igneous rock after melting. Igneous rocks are also transformed under the influence of pressure and heat. The collection of these changes and transformations of states is called stone cycle.[3]

Weathering attacks hard and solid rock in the beginning. This type of rock is either formed by the cooling of lava on the surface of the earth or it is an igneous rock that was formed under the surface of the earth and later emerged due to the erosion of its covering surface. The final products of weathering are materials that are used in the formation of new rocks (sedimentary, metamorphic and even igneous).

Landslides, running water and glacier ice are effective in moving materials from one place to another. In an ideal cycle, these materials end up on the bottom of the oceans. Petrification processes solidify the layers of soft mud, sand and gravel that are placed on the ocean floor and form sedimentary rocks.

If the cycle continues without interruption, these newly formed rocks on the ocean floor will gradually be buried deeper and deeper and will be affected by the pressure caused by the weight of the overlying rocks, temperature and forces caused by the earth’s movements. Under these new conditions, sedimentary rocks may change and become metamorphic rocks. If the temperature and pressure continue to increase, these metamorphic rocks will eventually lose their identity and become magma after melting. The cooling of this magma will cause the re-formation of igneous rock. In this way, a complete cycle is completed.

It is possible to interrupt the complete stone cycle at different points. For example, an igneous rock that is formed under the surface of the earth, may never be exposed and due to the lack of weathering, it will never turn into sediments. On the other hand, it is possible that the same rock is subjected to high pressure and temperature and directly turns into a metamorphic rock without passing through the intermediate sedimentary stage. The interruption of the complete cycle occurs when the sediments, sedimentary rocks or metamorphic rocks, continue their way in the complete cycle and enter the next stage, are attacked by weathering.

The stone cycle was probably first proposed in the late 18th century by James Houghton. He says in his book Theory of Earth; So we are led in a direction where we can observe the circulation of matter in this sphere. A circulation that expresses the performance of a kind of economy in the system of nature. One of the states of the earth is the state of growth and increase, and the other state is the state of decline and decay. Therefore, the world is destroyed in one corner and rebuilt in another corner, and the processes by which the world is destroyed are as obvious in the eyes of science as the processes that reconstruct it.[4]