Understand the rock strata and select the correct drilling and mining tools.

A rock is a solid assemblage of one or more minerals and natural glass with a stable shape. A rock composed of one mineral is called a monoreite; Rocks composed of several minerals are called polymineral rocks. Rock is one of the materials that make up the Earth's crust and is the main component of the Earth's lithosphere. Liquids without a definite shape, such as oil, gases such as natural gas, and loose sand and mud, are not rocks. Rocks can be divided into magmatic rocks, sedimentary rocks and metamorphic rocks according to their formation reasons.

Magmatic rocks: 

It refers to the magma in the process of rising to the surface, due to the heat loss gradually through the process of differentiation and condensation of the rock, because it is related to volcanism, so it is also called igneous rock. Extrusive rocks are called extrusive rocks, and those that condense under the surface are called invasions. The different crystallization degree, particle size and shape of the minerals in the rock, as well as their relationship with each other, form the different structure of magmatic rocks. The different arrangement, configuration and filling ways of minerals in the rock in space form different structures of magmatic rocks. 

① Extrusive rocks generally have primary porosity and joint development, irregular occurrence, large thickness variation, very uneven lithology, lower strength than intrusive rocks, strong permeability, such as rhyolite, trachyte, andesite, basalt, pyroclastic rock. 

② Intrusive rocks: according to the depth of formation, intrusive rocks are divided into deep rocks and shallow rocks. Plutonic rocks, such as granite, syenite, diorite and gabbro, often form large intrusions such as batholith. The lithology is generally simple, with medium to coarse granular structure, compact and hard, small porosity, weak permeability and strong water resistance. Shallow rocks are mostly produced in the state of bedrock, dike, dyke, etc., sometimes intersperse with each other, with fine particles, high rock strength, and not easy to weather. However, the contact parts between these small intrusions and the surrounding rock mass have uneven lithology, joint fissure development, rock fragmentation, severe weathering alteration, and increased permeability, such as granite porphyry, diorite porphyrite, diabase, and dyke rock. Magmatic rocks usually have homogeneous and isotropic characteristics (except for some extrusive rocks), and the mechanical properties are usually relatively high, among which the strength and weathering resistance of deep rocks are the highest, followed by shallow rocks and volcanic extrusive rocks.

Sedimentary rocks

It is a layered rock formed by weathering, biological action, volcanism and other geological stresses under the surface conditions of the crust, through a series of geological processes such as transport, deposition and diagenesis. There are four structural types of sedimentary rocks: clastic structure, argillaceous structure, granular structure and biological structure (including biological remains). The structure of sedimentary rock refers to the spatial distribution and arrangement of each component of the rock. The main structure of sedimentary rock is bedding structure, plane structure, and chemical structure (nodules, sutures, etc.) and biogenic structure (fossils, etc.). According to the composition, structure, structure and formation conditions of sedimentary rocks, they can be divided into clastic rocks (such as conglomerate, breccia, sandstone, siltstone), clay rocks (such as mudstone, shale), chemical rocks and biochemical rocks (such as limestone, dolomite, siliceous rocks, marl, etc.). Rock, coal, graphite and petroleum are often formed during the formation of sedimentary rocks.

Metamorphic rocks

Magmatic rocks, sedimentary rocks and even metamorphic rocks are affected by high temperature, high pressure and chemical composition in the crust, and the new rocks formed after the mineral composition and structural structure changes in the solid state are called metamorphic photometamorphic rocks. The mineral composition of metamorphic rocks in addition to the minerals of the original rocks before metamorphism, such as quartz, feldspar, mica, dolomite, etc., there are also minerals produced by metamorphism, such as talc, chlorite, argillite, garnet, etc. Common metamorphic rocks 

(1) phyllite is mostly formed by clay rock metamorphism, soft texture, low strength, poor weathering resistance, easy to weathering and spalling, and easy to collapse along the schistosity tendency. 

(2) The schist has lamellar structure and blastoblastic structure. Schistosity is generally relatively developed, the content of flake minerals is high, the strength is low, the ability to resist weathering is poor, it is easy to weathering and spalling, and it is easy to fall along the schistosity. 

(3) Gneiss has a typical gneisse-like structure and generally coarse grains. It can be formed by metamorphism of magmatic rocks or sedimentary rocks. The strength is higher, if the mica content increases, the strength decreases correspondingly. Because of the schistosity structure, it is easy to weather. 

(4) SLATE is formed by shallower regional metamorphism of shale rocks. It has blastopelitic structure and plate-like structure. It is widely used as a building material because it can be split into slabs along the slab. 

(5) Marble block structure, the main mineral composition of calcite, hydrochloric acid strong foaming, can be distinguished from other light-colored rocks. Medium strength, easy mining and processing, is a good building decoration material. 

(6) Quartzite structure and structure are similar to marble, from the pure quartz sandstone metamorphism, high strength, strong resistance to weathering, is a good building stone, but the hardness is very high, mining and processing difficult. A variety of metallic ores and non-ferrous ores are formed through magmatic activity or metamorphism.

Three distinctions

1) Magmatic rocks are formed by the cooling and solidification of magma. It is characterized by distinct mineral crystals. Such as granite quartz, feldspar and other mineral crystals; Basalt is often black and has porosity structure. Andesite: any of a wide range of extrusive rocks, including plagioclase, hornblende, etc.

2) Sedimentary rocks are formed on or near the surface by weathering, transport, deposition, etc. There are bedding structures, like shale can see obvious stratification; It may also contain fossils, such as ancient fossils in limestone. For example: sandstone, shale, limestone, etc.

3) Metamorphic rocks are formed by the metamorphism of existing rocks (magmatic rocks, sedimentary rocks, etc.) under the conditions of high temperature and pressure. Its mineral composition and structure will change, for example, marble is metamorphic from limestone, harder than limestone, coarser grains. For example, Quartzite.

Understanding rock strata classification is fundamental to selecting the correct drilling and mining tools. By matching bit type and cutting structure to the specific characteristics of magmatic, sedimentary, and metamorphic formations, operators can optimize penetration rates and extend tool life.

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