Stalactite

Here, the stalactite is formed on quartz sandstone, and the white stalactite is elegant and beautiful against the red rock wall.

Stalactite

Stalactite, also known as stalactite, refers to stalactite, stalagmite, pillar and other different forms of calcium carbonate precipitates formed in the long geological history and specific geological conditions of caves in carbonate areas.

The formation of stalactite usually takes tens of thousands or hundreds of thousands of years. Because of its long formation time, stalactite has important research value for ancient geological investigation. In limestone, water containing carbon dioxide seeps into limestone crevices and reacts with calcium carbonate to form water-soluble calcium bicarbonate. When water containing calcium bicarbonate drips down from the cave top, it decomposes and reacts to form calcium carbonate, carbon dioxide and water. The dissolved calcium bicarbonate becomes a solid again (called solidification). From the top to the bottom, it is called "stalactite". It can be used as medicine.

Guangxi and Yunnan are the main provinces with the most abundant resources of stalactites in China. The stalactites produced in Guangxi and Yunnan are lustrous and unique in shape, which have high appreciation and collection value and are deeply loved by people. "Curling" and "Double Dragons" by Fuchun River written by Biye: "there are stalactites everywhere in the cave, moist and fresh. Some are like jade pillars from the top to the ground, some are like rain clouds hanging in the air, and some are like white waves surging into the sky. It's really magnificent."

In limestone, water containing carbon dioxide will dissolve calcium carbonate when it seeps into cracks in limestone. When the water that dissolves calcium carbonate drips down from the top of the cave, due to the evaporation of water and the escape of carbon dioxide, the dissolved calcium becomes solid again (called solidification).

Formation process

Stalactite is formed by the deposition of calcium carbonate and other minerals.

Limestone is a kind of calcium carbonate rock, which is decomposed by water containing carbon dioxide to form calcium bicarbonate solution. The chemical equation of this reaction is as follows: CaCO ₃ (s) + H ₃ o (L) + CO ₃ (AQ) → Ca (HCO ₃) Ψ (AQ) solution goes down the rock until it reaches the edge. If the rock is at the top of the cave, the water will drip. When the solution comes into contact with air, a reverse chemical reaction occurs and calcium carbonate is precipitated. The reverse chemical equation is as follows: Ca (HCO ₃) Ψ (AQ) → CaCO ₃ (s) + H ₃ o (L) + CO ₃ (AQ) the average annual growth rate of stalactite is 0.13MM. The rapidly growing stalactites are often rich in calcium carbonate and carbon dioxide in aqueous solution, and flow very fast. The stalactites can grow by 3 mm per year. Each stalactite starts with a drop of water containing minerals. When the water drips down, it leaves a thin circle of calcite. The next drops continue to leave New calcite circles. Eventually, these calcite rings form very thin (0.5mm) hollow tubes, commonly known as "soda tubes.". Soda pipes can be very long, but very fragile. If they are blocked by debris, water will flow through the outside and precipitate more calcite, forming a cone-shaped stalactite. Similarly, the falling water droplets precipitate more calcite after reaching the ground, and finally form round or conical stalagmites. Unlike stalactite, there is no hollow soda tube in the process of stalagmite formation. If the time is long enough, stalactites and stalagmites will fuse together to form stone pillars.

Chemical origin

Karst caves are distributed in the mountains composed of limestone. The main component of limestone is calcium carbonate. When encountering water with dissolved carbon dioxide, it will react to form calcium bicarbonate with greater solubility. When water with dissolved calcium bicarbonate is heated or when the pressure suddenly decreases, the calcium bicarbonate dissolved in the water will decompose, regenerate calcium carbonate, deposit and release carbon dioxide. When the water at the top of the cave seeps down slowly, the calcium bicarbonate in the water reacts as mentioned above. Some are deposited at the top of the cave and some at the bottom of the cave. Over time, stalactite is formed at the top of the cave and stalagmite is formed at the bottom of the cave. When the stalactite is connected with the stalagmite, the stone column is formed.

experiment:

Take a large teacup (or test tube), dissolve a small amount of hydrated lime (i.e. calcium hydroxide) in water, and let it stand for a moment. The undissolved hydrated lime will deposit at the bottom of the cup. At this time, the cup is divided into two layers: the upper layer is as clear as water, which contains dissolved calcium hydroxide; the lower layer is lime milk, which is turbid. Carefully pour the upper layer of clear lime water into a test tube for about 2ml, and then blow air into the lime water through a glass tube (which can also be replaced by a plastic tube, a straw for drinking soda). Because the human body exhaled gas contains carbon dioxide, so limewater and it had a chemical reaction, formed insoluble in water white solid limestone, limewater turbid.

Calcium hydroxide + carbon dioxide → calcium carbonate + water

Ca(OH)

If we continue to blow into the muddy limewater, it will soon become clear again. This is due to the interaction between carbon dioxide and calcium carbonate to form calcium bicarbonate which can be dissolved in water. Therefore, the turbid liquid will become clear with the dissolution of precipitation. If the clarified solution is heated, the calcium bicarbonate will be transformed into insoluble calcium carbonate, and the solution will become turbid again.

Calcium carbonate + carbon dioxide + water → calcium bicarbonate

CaCO

In nature, many limestone zones (mainly composed of limestone) have formed strange peaks and caves for this reason, and stalactites and stalagmites have grown.

Stalactites and stalagmites are quite different. One is like an icicle under the eaves in winter, hanging down from the top; the other is like a bamboo shoot "emerging" from the ground in spring.

There are many cracks on the top of the cave, and water droplets constantly seep out of each crack. Whenever the water evaporates, some calcareous sediment will be left there. One drop, two drops, three drops With the appearance and volatilization of water, the limestone on the top of the cave accumulates more and more, and finally forms a nipple - this is the "childhood" era of stalactite. Later, the nipple was covered with layers of calcareous matter, so that it became longer and longer. Some stalactites can reach several meters in length.

Stalagmites are stalactites' close companions. When the water drops from the top of the cave, the calcareous matter also deposits on the ground. In this way, the stalagmite grows up against the stalactite. It can be said that stalactite is "Sir" and stalagmite is "posterity". But the stalagmite has a large base, which is relatively stable and not easy to break, so its "growth" speed is often faster than that of stalactite. The maximum height of the stalagmite can reach 30 meters, like a "stone tower" growing out of the flat ground.

Sometimes the stalactite growing from the bottom is connected with the stalagmite growing from the top to form a stone column. It is thick at both ends and thin in the middle. People who don't know the details of the stalactite still think it was chiseled out. In many limestone caves, most stalactites and stalagmites are not connected together; that is because the stalactite is broken, or too much lime blocks the path of the water drop, and the water drop is forced to change its path to another place, and a new stalactite grows. In this way, stalactites and stalagmites will not meet.

Groundwater plays a decisive role in the formation of stalactites and stalagmites. Every place where it flows will leave traces, or a ditch or a hole, or a stalactite, or a stalagmite, or a stone pillar; put them together to form a "forest", "bead curtain" and other wonderful scenes. This phenomenon is often encountered in daily life: for example, the bottom of the kettle used to boil water is often covered with dirt. Take out some, add some vinegar, you will see a lot of bubbles. This is because tap water contains calcium bicarbonate, magnesium bicarbonate, etc. some components of scale are their decomposition products when heated, such as calcium carbonate and magnesium hydroxide.

Because the temperature in nature is not as high as boiling water, the formation of stalactites and stalagmites is not so fast. It was formed after tens of thousands of years of long-term deposition and continuous changes.

Drug use

[English name] stratitum

[alias] Shi Zhong Ru, di Ru Shi, Shi Ru Zhong, Gong Ru, Xu Zhong, Lu Shi, e Guan Shi, Xia Shi, Huang Shi Sha.

[explanation] it grows in the shade of the cave. It is formed by the flow of mountain liquid. It is connected with the air. It is six or seven inches long, like a goose feather tube. It is white and slightly red. The milk is dripping continuously. It can be taken by bamboo tube.

[source] this product belongs to calcite group of carbonate minerals, mainly containing calcium carbonate (CaCO3). After harvest, remove the miscellaneous stones, wash and dry.

[character] the product is a bell shaped aggregate, slightly conical or cylindrical. The surface is white, grayish white or brownish yellow, rough and uneven. Body weight, hard quality, flat section, white to light gray white, light observation with flashing star like light, near the center often has a round hole, there are many light orange yellow concentric ring layer around the round hole. Odorless, slightly salty.

[identification]

Chinese PinYin : Zhong Ru Shi