Petrography is a branch that belongs to petrology and general geology, and that basically deals with the description of rocks. The description consists of analyzing the mineral composition, the texture, the structure and all the physical properties that the rocks have in order to give them a name and a classification.
Importance and applications of petrography
Thanks to petrography techniques, geologists can define and classify different types of rocks by analyzing all their physical and visual properties.
Defining and classifying a rock type using petrography has wide applications, for example it is useful to define the rock types to be used as Construction materials, sedimentary rocks that can store water or hydrocarbons, determine rocks that may be associated with different mineral deposits and even define rocks that serve to study the earth’s past.
Also, thanks to petrography, suitable types of rocks can be defined where large constructions such as bridges, buildings and our houses will be established.
Geologists directly classify rocks in order to define suitable geological environments for mineral exploration, hydrocarbon exploration, geohazard application, and engineering.
Mine engineers use petrographic analysis to stabilize slopes in open pit mines and tunnels in underground mines, in addition, there are certain lithologies associated with metallic and non-metallic deposits.
Volcano geoscientists study the petrography of rocks in order to define geological formations associated with recent volcanic eruptions and thus create prevention plans.
Geotechnical engineers analyze the types of rocks and their petrography to define the stability and mechanical behavior that they will have on roads and slopes.
Petrography techniques
Petrographic analyzes are techniques that are performed with naked eye analysis. However, today’s technology allows even more detailed rock analysis using petrographic microscopes and thin slices.
Macroscopic petrography
Geologists to define and classify a rock by analyzing all its characteristics and properties use basic tools such as a magnifying glass, a hardness pencil, 10% hydrochloric acid, a magnet, and a geologist’s hammer.
The magnifying glass is used to analyze and define the different types of minerals that make up the rock, the texture, structure, color, weathering and other visual properties that are identified in the rocks.
The hardness pencil is used to define the Mohs hardness of the minerals that make up the rocks. Hydrochloric acid is used to identify carbonate minerals such as calcite.
The magnet is used to discover magnetic minerals such as magnetite. Finally, the geologist’s hammer is used to break the rocks and thus be able to analyze them and even take them for further laboratory analysis.
Microscopic petrography
The petrographic technique of analysis using a petrographic microscope is used to perform the same analyzes that a geologist does using a magnifying glass, but in more detail. In addition, it has more advantages because other more advanced optical properties such as cleavage, refractive indices, colors in natural light and polarized light, pleochroism, etc. can be analyzed. This technique is called microscopic petrography.