Seven white marble columns from the Old Summer Palace return home! Is white marble "jade"?

On October 13, the State Administration of Cultural Heritage learned that seven stone pillars had recently returned to their original location, the Old Summer Palace. This is another batch of important cultural relics that have been lost overseas and returned to the Old Summer Palace after the bronze statue of the horse head, which has opened a new chapter for the protection and utilization of the Old Summer Palace cultural relics and their exhibition in museums.

The 7 returned stone pillars are all made of white marble, with a total height of about 80-92 cm. The front is decorated with mainly Western carvings such as foreign flowers and shell patterns, while the bouquets in the vases on the side are mainly traditional Chinese flowers with auspicious meanings, such as peony, magnolia, lotus, chrysanthemum, etc. The carving method of the angular cloud patterns and the crabapple lines of the windows are the same as the balusters and railings of ancient Chinese buildings, reflecting the cultural connotation of the combination of Chinese and Western cultures.

We often see or hear the building material "white marble" in gardens, mausoleums, and palace buildings. So, is white marble jade?

In fact, white marble is not actually "jade", but a kind of white marble.

Marble, metamorphic

Marble gets its name from Dali in Yunnan, but this rock is produced far more than just the Dali area. The white marble (white marble) of the Forbidden City and Tiananmen Square was mined from Fangshan in the western suburbs of Beijing.

In addition to the beautiful white marble, there are many marbles that are loved for their colorful colors and unique patterns. They are neither directly created by magma nor simply deposited by wind and water, but the product of the combination of the two.

In other words, they are "metamorphosed" from fragile limestone.

Limestone layers underground are sometimes invaded by hot magma along cracks. Under high temperature, the small particles of calcite that make up the limestone will dissolve and crystallize again, forming larger calcite particles. The new rock they form is marble.

Like marble, igneous rock or sedimentary rock undergoes changes in temperature, pressure and other conditions underground, and becomes a new rock while remaining basically solid. This process is called "metamorphism". The new rock created by metamorphism is called metamorphic rock .

Metamorphic rocks, why do they change?

In the entire crust, metamorphic rocks account for about 27% of the total rock volume and are distributed both on the continents and on the ocean floors.

Magma intrusion alone cannot "change" so many rocks. Geological activities in the crust and deep inside the earth have also played a role in this process. Some of these are small and some are large.

If the scope of metamorphism is only a few square meters to a few square kilometers, it is called " local metamorphism ". The main force that creates marble - magmatic activity is a kind of local metamorphism.

If it is " regional metamorphism ", a more powerful force must be used - the tectonic movement of the earth's crust. The continental drift, sea-land changes, and mountain formation on the earth's surface are all masterpieces of tectonic movement. It is even easier to let it process rocks.

Metamorphic experience, mineral secrets revealed

If you want to know how severe the metamorphic environment a metamorphic rock has experienced is, you can look for clues in the minerals it contains . For example, minerals such as andalusite, cordierite, and biotite are formed in an environment with high temperature but low pressure .

In the strata no deeper than 10 kilometers underground, the pressure on the rocks is not very strong, but if invaded by magma, the rocks will be heated to over 500°C. Minerals formed under such metamorphic conditions are generally not afraid of high temperatures, and minerals such as andalusite and cordierite are used as refractory materials.

Low temperature and high pressure environment often forms blueschist, green chalcanthite, etc. If there are a lot of garnet and pyroxene in the metamorphic rock, it is likely to have been subjected to high temperature and high pressure deep in the stratum.

Comprehensive sources: Xinhua News Agency, State Administration of Cultural Heritage, China National Geographic