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What do you know about the stories about shells?

If we go to the seaside, on the beach, we can always see all kinds of shells, small and big, colorful, white, and broken out of shape. There are fan-shaped, spiral-shaped, in short, thousands of shapes. I think if we go to the seaside, we will always step on the beach and pick up a pile of shells as gifts for our friends, relatives, loved ones and so on. When you are holding a shell, do you think about anything?

Seashells, as the name implies, the shell of shellfish (literally). The shell is the shell of a mollusk that lives near the water and is formed by the secretion of a special glandular cell of the mollusk. It is a kind of calcium to protect the soft body, and has a unique multi-scale, multi-layer "brick-mud" assembly structure. The shell is mainly composed of about 95% CaCO3 and about 5% organic matter. This 95% is mainly inorganic phase, such as calcite, aragonite and so on.

Calcite may be known to everyone, here is a brief introduction: calcite is a kind of calcium carbonate mineral, is the most common natural calcium carbonate mineral, calcite has a variety of crystal forms, granular, massive, fibrous and so on. Most of its colors are colorless and transparent, trigonal crystal system, three groups of extremely complete cleavage, glass luster, and the hardness is 3 in the Morse hardness scale. Calcite, as the most common mineral in the ocean, is created in every corner, with coral reefs and mollusk shells.

Massive calcite (source: Jintou net) is talking about seashells. How come it comes to minerals? let's come back for a while.

When it comes to seashells, we have to say about the ancient usefulness of seashells, and those who have studied middle school history should be clear about the development and origin of human money. As early as four thousand years ago, that is, in the Shang Dynasty, money had already stepped onto the stage of history. At this time, people often tied the toothed shellfish together with string and tied them around the waist as a medium for material exchange. The earliest currency was called Baby. Ha). In other words, the shells in ancient times were money and money, and Grandpa Mao had the same status. Special tooth shellfish are relatively rare, so they have the advantage of acting as money. Shells are so beautiful and valuable!

In ancient times, the history of marine molluscs (such as shellfish) is much earlier than that of humans, and their distant ancestors can be traced back to the Cambrian small shell fauna. By this time you should be able to understand the second function of shells-fossils. Through the study of shell fossils, we can understand the evolution history of marine molluscs and provide a clear transition line for the evolution of life. With regard to the small shell fauna, this is another very famous biota, which is no longer unfolded, as long as it is known that the small shell fauna is the distant ancestor of shellfish.

Fossils of small shells in North China (source: China Science Popularization Network) the role of shells is over. Ah, no, the meat in shells is also very delicious, such as raw oysters and mussels (drooling). Stop talking about food.

What should be discussed is why there are so many shells in the sea. When it comes to this, we have to first discuss the distribution of elements in sea water. There are twelve major elements, such as Cl, Na, Mg, S, Ca, K, Br, C, Sr, B, F and Si. Of course, you have to consider water, that is, H and O. We know that through these elements, the more stable solid compound composition is calcium carbonate (CaCO3). Then the elements that molluscs can use, including the strongest building material, calcium carbonate, are determined by their own characteristics.

The beautiful ocean (source: the author shot in Hainan) extends to the rock level, the most common marine rock is limestone, including fossil limestone, bamboo leaf limestone and so on, which represent a typical marine deposit. There is another special type of limestone, which is biological limestone, including biological skeleton limestone and biological shell limestone. Biological framework limestone is mostly reef limestone, limestone formed by biological reef, this kind of limestone is porous and easy to form a good reservoir. Biological shell limestone is limestone with high content of shell detritus. Some time ago, there was a hot search of Weibo "the toilet of Guiyang Airport is full of fossils". The protagonist of the event is shell limestone. The fossil has been identified as the Silurian five-room shellfish. What needs to be reminded here is that fossils do not have to be protected, but some fossils can be used for other purposes, ornamental collection and so on.

There is also a very inspiring story about shells. The protagonist of the story is Geerat J. Vermeij, an academician of the American Academy of Humanities and Sciences, who is a professor of geology at the University of California, Davis. This is a blind scientist who has been completely blind since the age of 4. He has used his hands instead of eyes to study shellfish, plants, crabs, marine mammals and so on. He has published six books and nearly 280 research papers. When I was a graduate student, I successfully entered Yale University by knowing seashells by hand. Do you think he can only talk on paper? No, which of the dry geology and biology doesn't come out of the field? When you go out in the wild all the year round, it is hard to avoid a lot of pain. In 1993, the first edition of his first book, "the Natural History of shells", he and shellfish were like Boya and Ziqi, in which he was "good at it". With regard to his story, you can search it for yourself.

Vermey and his shell (photo source: fruit shell) so delicious (the meat inside), good-looking, fun, and scientific research value of the shell, do you like it?

This article comes from the official account of Wechat: stone popular Science Studio (ID:Dr__Stone), written by Xingyu, edited by Liu Yuling

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