How are the patterns and colors of granite formed?

Few people in this world dislike granite. For Chinese people, granite landforms can be seen in many famous mountains in China. In human society, granite has become one of the most widely used indoor and outdoor building decoration materials due to its brilliant colors, stable chemical properties, and excellent physical and mechanical properties. Many magnificent domestic construction projects, such as the Great Hall of the People in Beijing, the National Grand Theater of China, the Nanjing Zhongshan Mausoleum, the historical buildings on the Bund of Shanghai, the Luoyang Bridge and the East West Tower in Quanzhou, the the Potala Palace in Lhasa, and the German buildings in Qingdao, also have extremely rich granite elements.

As an important petrology symbol that distinguishes the Earth from other planets in the solar system, granite is like an art gallery of nature. No matter what kind of granite, it has amazing beauty. If we simply distinguish by patterns and colors, there are hundreds of types of granite products commonly used by humans in the world, which can be said to be very rich. Common granite products have basically no colored stripes, only colorful spotted patterns. It is the uncanny craftsmanship of nature that creates all the forms of granite.

Billions of years ago, the Earth was formed by the fractionation, collapse, and condensation of primitive solar nebulae. Every celestial particle that falls on the primordial Earth has a high amount of motion energy, which is converted into thermal energy due to impact. Later, this thermal energy is preserved due to the increase in external weight and internal compression of the Earth. In addition, the accumulation of heat generated by the decay of radioactive elements such as uranium, thorium, and potassium causes the Earth to heat up, causing the melting of most of the material inside the Earth.

Due to the fact that the crust of the primitive Earth was rich in iron, magnesium, and silicon, the initial melting only produced basaltic magma, which later formed the basaltic layer of marine landforms. But when the basaltic rock undergoes melting again, the light matter with low density continuously rises and accumulates, gradually forming silicoaluminal magma, which is the granite layer mainly composed of silicoalumina that forms the landforms of continental regions. As time went on, the preserved continental crust was melted again and again, making its composition continue to increase in the direction of silicoalumina, while the remaining mafic returned to the mantle in an appropriate way.

This process is repeated, so that the continental crust of the earth continues to develop in a stable direction, and finally forms today’s earth topography. It is precisely during the process of geological changes that the main elements such as silicon and aluminum are fully mixed by melting and the participation of water. After cooling, they form uniform porphyritic textures. Due to differences in the original composition of melts, cooling rate of magma, nucleation rate of crystals, pressure changes, amount of volatile substances, and fluid viscosity in different regions, various types of granite with different appearances have also been formed.

From the perspective of modern mineralogy, we believe that granite is mainly composed of feldspar with silicon and aluminum as the main elements, quartz, mica containing iron and magnesium, hornblende, pyroxene, olivine, serpentine, etc.

Among them, orthoclase is usually gray white, yellowish brown and flesh red, plagioclase is usually gray white, quartz is usually transparent or gray, biotite is usually black, brown, red and green, and pyroxene and hornblende are usually black, dark green and dark brown. Generally speaking, black, dark green and chartreuse granites contain more olivine, pyroxene, hornblende, biotite, etc., and almost no quartz and feldspar; The main components of white, flesh red, grayish red, light pink, gray, and grayish white granite are feldspar and quartz. Dark substances such as biotite are more common, while hornblende and other minerals are relatively rare.

Like Shijing Rust Stone, it is due to the weathering and decomposition of iron containing minerals that generate iron oxides and hydroxides that fill the pores and mineral cleavage of the rock, resulting in a rust yellow color of the rock. In addition, when the crystal structure of minerals is defective, the color of granite may also change. For example, potassium feldspar is light flesh red and plagioclase is gray white. When the crystal structure is defective, potassium feldspar can be bright red and dark red, and albite can be light cyan.

When the chemical composition of minerals contains chromogenic ions, the color of the rock may also change. For example, when some K in potassium feldspar is replaced by Rb, it will turn blue-green, which is the origin of Tianhe stone, and granite rich in Tianhe stone also has a unique flavor. Of course, with the continuous mining of granite stones produced by the same mine, there will also be certain differences in color between the surface granite and the deep granite. The color of granite will also be slightly different with different processing technologies. For example, the color of smooth surface is always darker than that of litchi surface or other rough surface.

Nature is always creating surprises and miracles for humanity, perhaps just a plain and unremarkable piece of material. When a sawing machine cuts it open, what suddenly appears in front of people is a beautiful texture like landscape painting. After thousands of years of sedimentation, nature endows natural stone with rich and colorful colors and ever-changing textures. No matter when, this magnificent creation created by nature is more spiritual than the works showcased by painters with thick ink. I believe that when a stone that has been passed down for hundreds of millions of years encounters the craftsmanship of the new era, there will inevitably be a dazzling spark between the old and the new.

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